I have a single key for my 74 Elan Plus 2 and cannot find anywhere to buy a blank. My local key shop is of no help which is surprising.
The key is a Taylor D80 with a K underneath that if that matters. Google searching does not show up any obvious places to buy this key so I’m thinking there must be another equivalent.
Assuming you’re talking about the ignition key, RD Enterprises in PA has them: www.rdent.com and do a search for “WS2” Key Blank
I got one from them recently and it works great in the slot. However, an issue (at least on my +2) is that the plastic on the key grip is large enough where it hits the dashboard that overhangs the ignition key slot and prevents actually starting the car. So I had to cut part of it away with a Dremel. (You can’t just remove the plastic that’s overmolded on the metal unfortunately).
RD also sells door keys if that’s what you’re looking for.