it's extremely hard to find.. and very expensive usually when you do find it. I hope you are aware that it is pretty much totally useless?
you will need to stuff 4 or 6 of the quite expensive 32 mbit dram carts into it, and then are still limited to roms <24 MB (not that many), not to mention that it takes ages to transfer the game (from disc would literally take half an hour or more).