http://www.mks.purespace.de/technical/sgblink.htm

Has anyone tried this? Since the Gamecube Game Boy player is so expensive nowadays, this seems like a much more realistic alternative. Would anyone be willing to do this to two Super Game Boys I have?

I could do it for you.

Not to steal any thunder from Nitro, but if you can get your hands on a Super Gameboy 2, they already come with a GBC/GBP link port.