That is precisely the quest Jose Torres, AKA BleepBloop, Creator and Administrator for 8bitcollective is on. BleepBloop quickly explains himself and his plans as follows.
"So I guess I should tell you guys a little about myself before we get started. I'm entering my third year this fall in the electrical engineering program at the Rochester Institute of Technology in New York. Ever since I learned about gameboy music, overpriced LSDJ cartridges, Nullsleep and reigner ziegler. I've been on a mission to build a cartridge that is affordable and easy to use."
He goes on to explain what he's been working on, some examples and pictures, and some more technical things. If you want to check out his ongoing work, head over to the thread at 8bc, and if you are a musician looking for an affordable LSDJ solution, consider sending a small donation his way as well.