It looks like gex will sell you one for the princely sum of $23 (Canadian? US?)https://www.pcenginefx.com/forums/index.php?topic=21202.0
Well a pce tap would be the cheapest way to go, no adapter needed. Should be able to score one of those for $15-ish. But if you prefer the more expensive route I have a boxed u.s. one I could probably part with.