@sega16: oops! Er, I guess I didn't read your post very well. Didn't realise YOU were the guy who made that cart! Hope I didn't come off too harsh.
Someday I hope someone gets as far as AtariAge and their Melody boards. With AtariAge you can literally online order your cart. Just send the binary and they have the boards ready. No need to make anything as expensive as a Everdrive clone. Just something easy for one-off carts.