Reddit mentions of CaseCrown Horizontal Mobile Messenger Bag (Black) for Microsoft Surface/Microsoft Surface Pro

This is my bluetooth mouse: http://www.amazon.com/Razer-Orochi-Mobile-Gaming-Mouse/dp/B00AAS88K6/ref=sr_1_2?ie=UTF8&qid=1382404906&sr=8-2&keywords=razer+bluetooth+mouse It has an attachable cord to increase the DPI up over the bluetooth standard if you need more speed or persision. I also use this bag http://www.amazon.com/gp/product/B009RV2EOI/ref=oh_details_o07_s00_i00?ie=UTF8&psc=1 and it fits perfectly and is light and durable. Looks as good as the day I bought it!

For daily transport I use a Messenger bag. This one in fact. http://www.amazon.co.uk/dp/B009RV2EOI

For occasional case use I use a cover that I can put on and off that allows for a bit more protection. It's decent quality, but virtually doubles the weight of the Surface. http://www.amazon.co.uk/dp/B00M43LWU8

On a daily basis though it spends most of the time just being used, on my desk, fully nude and spread out. ;)

I've been using messenger bags for my Surface devices (to be fair, laptops and ultrabooks before them), and I currently carry SP3, SP4, or Book depending on what I'm doing. I use CaseCrown bags, and since you listed an Amazon link I'll share the one I have currently via Amazon (I have the "black stealth" color scheme):

http://www.amazon.com/CaseCrown-Messenger-Black-Microsoft-Surface/dp/B009RV2EOI

EDIT: For reference, I don't put the Book in this bag, as it doesn't quite fit (I have a laptop bag I use when I need to haul that thing, and I'm usually carrying a lot more), but I use the Pro 4 (and Pro 3 before it) primarily to/from work, and everything goes in here nicely. My next bag will probably be this, though, as it will fit a book too:

http://www.amazon.com/MacBook-Laptop-Casecrown-Canvas-Horizontal/dp/B013J8M36I

http://www.amazon.com/gp/aw/d/B009RV2EOI

I have this, inexpensive but very functional. I can easily fit a mouse, 2 external HDDs, an external DVD drive, a legal pad and a handful of memory cards/flash drives. It has holders for pens, I like it a lot.

I have the [MoKo Slim-fit Case for Surface Pro] (http://www.amazon.com/gp/product/B00C8T7O4Q/ref=oh_details_o00_s00_i01?ie=UTF8&psc=1) and I really like it- although I'm not sure if it will give you as low of an angle as you are looking for. It has 3 different angles it can sit at, and if you ask me the lowest one is fine for writing on. Cool color options as well if you are into that! After writing all that I noticed you may not have a surface pro and the case I just mentioned is specifically designed for the pro. After some searching I also found the Fintie Folio Case for Microsoft Surface RT which is cheap enough to merit a "blind buy". The pictures on Amazon show that this case offers a really low angle that I think will appeal to you.

One thing that I REALLY love is the CaseCrown Horizontal Mobile Messenger Bag. I know it isn't a case, but this bag is so great. It can fit your surface and any accessories you may have and then some! I use this bag every day to bring my surface from place to place (or to a friends house). It has effectively become my "man purse".