It looks like my local video game surplus guy (the guy who snagged me some N64 analog stick replacements) has a bunch of these. I got one to try it, and WOW! The sound is night and day, and the video is of course improved. My Genny2 has a CD2 and 32X attached, and it is all mixed properly. Goodbye RF! I've never seen these anywhere else. For all I know they are common as hell in the US, but they are new to me.

I can get more (not sure how many) and I think they are about $8USD plus actual ship. Anyone who wants one, let me know!