Reddit mentions of Topeak Ninja Co2 Plus Ninja Cage Plus with Micro Airbooster & 2 Pieces 16G Co2 Cartridges

Storage:

For my gravel bike I use this seat bag, size large, it holds 2 tubes+patches, levers, a decent amount of food, keys, cash, etc. I carry a pump on my gravel bike, so without CO2, it holds a lot. For my road bike, I use a much smaller pack that fits patches, 1 tube, 2x CO2, levers, a CO2 nozzle, keys, and maybe 1 or 2 Cliff bars. Most smaller seat packs will let you cram all that in and then some. Just enough to fix 2 flats, so if you get a flat, you can decide whether to press on with a little bit of risk (hopefully you didn't pinch the tube doing the road repair, happens to me often, eaten by mosquitoes and rushing it), or go home. Go off Amazon reviews if you want a smaller pack, but if you want a larger one, I swear by that Topeak I linked.

For phone mounts, I use this Topeak Ridecase on both my bikes. You can replace your stem's top cap and convert it to a phone mount if your bike is aluminum/steel and uses one of those star nuts on the inside of the steerer, and if your bike is carbon and uses a compression thing for the top cap, don't attempt to use that, and instead use the included bar mount to put the phone mount right on your stem. I've only dumped my phone once out of about 1000 miles, on smooth pavement of all things, and I'm pretty sure I didn't slide the phone onto the mount until it clicked. My bad. I ride on bumpy gravel with tires at 85 PSI, just to give you an idea of how secure the phone is. Stays put. If you can find a Ridecase for your phone and your phone is water-resistant, 100% go with this, since you can put the phone right down the stem and conserve tons of bar space for bells/lights/even clip-on aero bars. The mount swivels to landscape, and it pivots up and down, it's seriously amazing.

Bottle holders are a dime a dozen, but I have 2 of these cheap ones on my gravel bike and I've never lost a bottle. You can find some novel bottle holders, if your bike has enough room underneath the water bottle bosses to accomodate - Here's a water bottle cage that fits 2x CO2 and a little pump, to free up some space. Spendy though. My other water bottle holders are all from local bike shop, all Specialized, and they're a bit better than the cheap Amazon ones, but they're plastic, and I've broken a couple by being reckless on my gravel bike, has a water bottle cage under the downtube by the chainring, and yeah, if I check a curb to see if I jump it, and totally nail the water bottle cage, it breaks. The cheap Amazon ones just get gouged and maybe bent lol. If you want something better than a cheap water bottle cage, I highly recommend checking them out at a local bike shop, since you'll be able to really get a feel for color and style and whatnot.

Top tube bags, I honestly don't use. These are actually really really handy for being able to access things like food while you're actively moving, but if you stop with frequency, you don't really need one. These things are kind of like seat bags, you can find any sort of thing with a fair amount of size and it'll have enough storage.

If you have water bottle mounts on your forks, gravel bikes usually, you might want to invest in a cargo cage of sorts, these are the holy grail of storage if you plan 100+ mile outings. I have Salsa Anything Cages on my gravel bike (can't find on Amazon) and I can stuff 1 spare chain, missing links, 6 tubes, and about 20 patches in it, and then top it all off with a few rags and a bunch of Cliff Bars. Like, I have so much flat repair and chain repair in this bag that I can stop and help anyone on the road and not worry about running out of my own supply. I consider this an absolute must for gravel excursions- even if you plan to return to home at the end of the day, you might be so far from home that your preparation or lack thereof can spell disaster, and you might bump into people that fell on bad luck. But yeah, if you tend to stray 50-70 miles from home on gravel, you absolutely need this. I've been 50 miles from home on sharp rocks, had to burn my last tube, and it was seriously a Hail Mary play, trying to get through those 50 miles back home with no sort of way to fix a flat. Don't ever get into that situation. You won't be able to walk your bike even 20 miles in 4 hours, and if it's dusk, you might not even see another cyclist in order to beg for help.

Edit: this is quite a wall of text, but yeah, those are my recommendations. I'd actually recommend just going to a LBS to figure out what sizes you need, try to purchase there, all the good stuff you'll find in a LBS and the prices for good stuff at a LBS is about the same as Amazon. Ask the people at the LBS for recommendations, tell them what kind of biking you do, see if they have what you need at the price range you want. If you go there and see a top tube bag you want, but you're not willing to spend 60 bucks on a Salsa or Revelate Designs bag, then go to Amazon and try to find similar size no-name generic stuff with tons of reviews. That kind of thing.