Sorry if it's not a direct solution/answer, but flash carts usually have built in cheat functionality (and built in cheat databases!).
If you avoid flashcarts due to ethical reasons, you can just choose to play only games that you have legit copies of. I bet the flash carts are within the price range of the cheat devices, anyway. So you're bound to spend the same amount of money either way.
Huh. Never actually thought of using it to cheat. I have a Gameshark 2.1 For GB/GBC and I just tried it on an AGS-101 (new brighter screen). It works, but it's pretty easy to bump it around while it's in there; Seems very loose. It screwed up Cosmo Tank when I bumped it sideways a bit while playing just now, tho the codes made me invincible - maybe the contacts just need to be cleaned.
I think I remember reading before I bought it that the GS-2.1 is the best cheating deviceson the DMG/GBC as far as hardware compatability goes (part of the reason I bought it). I used it on a Super Gameboy to transfer my progress in a Pokemon Yellow Gameboy cart over to another cart using some NO$GMB emulator hex trickery and then swapped the hex addresses back to the original after repacing the battery and never touched it again (battery is happy and game progress is still intact more or less).
I 'd be happy to sell it to you for $5 plus shipping. It's loose (no box or instructions).
