They're just keycaps... Signature Plastics makes alps compatible stems. The offial Geek Hack key group buys used to include alps compatible versions (at the same price) back when ALPS boards were the thing.
The issue isn't availability, its critical mass. If you can get enough people for a group buy, then you can get whatever you want. But, no, there aren't any existing stock pils of ALPS keys to choose from that aren't vintage (that I know of). Good luck finding ANSI layout, too.