Reddit mentions of Retro-Bit SNES - Super UFO Pro 8 Game Saves & Backup Cartridge Adapter (UFO) - Super NES

You can get the Super UFO 8. It is a flash/backup cart and allows you to place super famicom games on top.
https://www.amazon.com/Retro-Bit-SNES-Super-Backup-Cartridge-Adapter/dp/B007O3MWVG/ref=sr_1_1?ie=UTF8&qid=1503320273&sr=8-1&keywords=super+ufo

I can post a list of options here, I use them to test rom images before I load them to my repro carts:

Super UFO 8 (30-50 USD) :
Cheap, and basic, get the job done. Works with most clones. Uses software from about a million years ago; no, I'm not joking. It runs the same software that was on the old late 90's floppy readers updated to work with more modern hardware.
You have to be careful with savegames, there are some extra steps involved. Does not support ANY games that require specialized chips. Also, it smells funny (it has a strange chemical odor that never completely goes away). Theres a ton of these out there under a dozen or so different names, but if they are in this price range this is probably what your getting.
http://www.amazon.com/Saves-Backup-Cartridge-Adapter-Nintendo-Super/dp/B007O3MWVG/ref=sr_1_1?s=videogames&ie=UTF8&qid=1422038684&sr=1-1

Super everdrive (~150 USD):
Good interface and all the basic functionality is there and it works pretty much how you would expect. Works with some clones, but its a bit of a crapshoot. CAN support DSP-1 games if you have a dsp-1 chip installed on it (extra cost but worth it). Supply on these runs out sometimes, then they cost more for a bit. Doesn't smell funny.
http://www.stoneagegamer.com/super-everdrive-deluxe-na.html

SD2SNES (200-300 USD):
Creme-de-la-creme, all the basic functionality is there, and it has some nice bells and whistles. Solid interface. DOES NOT WORK RELIABLY WITH CLONES! USE A GENUINE SNES! Supports pretty much every special chip except for the SuperFX. Pricy, occasionally in short supply but generally you can get ahold of them without TOO much trouble. Doesn't smell funny.
http://www.stoneagegamer.com/sd2snes.html

I have or have worked with all 3 of these. feel free to ask if you have any other questions.

It’s a bit pricy but you could use this: Retro-Bit SNES - Super UFO Pro 8 Game Saves & Backup Cartridge Adapter (UFO) - Super NES https://www.amazon.com/dp/B007O3MWVG/ref=cm_sw_r_cp_api_i_mNu8Cb97YNQXV

Then the next cheapest adapter option that requires no modification at all is a Nakitek Game Saver + which will also allows you to save state your games. Alternative adapters would include the Innovation Super 8 (NES/Famicom adapter) and the Super UFO Pro 8 (an SD card based flash cartridge based on the old floppy disk copiers), but for the price that those two are going for these days, it would be much cheaper to get a SFC.

http://www.amazon.com/Saves-Backup-Cartridge-Adapter-Nintendo-Super/dp/B007O3MWVG

You should look into a battery backup system like this for the SNES and a DexDrive with a Gameshark following this guide for the N64

You don't need an SD2SNES.

Get a Super UFO Pro 8.

https://www.emuparadise.me/reviews/SuperUFO/

https://www.youtube.com/watch?v=kRQAz7uOafk

https://www.amazon.com/Retro-Bit-SNES-Backup-Cartridge-Adapter-Nintendo/dp/B007O3MWVG

This thing'll do the trick, too.

You can get something like this. It takes SD cards and it can connect to a PC via USB. There may be better choices than this one, I just did a quick search. They won't work with any games that use the SuperFX chip though.