Hmm, with the caveat that I'm going on at least a 12 month old memory, I think the one on the '68 Elan looks like that and AFAIK both cars use the same steering column.
Rimmer Brothers, a UK specialist for Triumph cars, list one on their site at £15 and apparently have them in stock, so most specialist suppliers should be able to get hold of one. They have a picture but it's from the underside so you just see the tabs and purple wire.
http://www.rimmerbros.co.uk/Item--i-GRID005792If you don't have the spring-loaded pencil connector I picked one up from Ebay UK last year for £5 and they're easily available. I was doing a similar thing to yourself in adapting another wheel boss to try a different sized wheel, I just drilled the hole and dropped the connector in - job done !
Brian