I never found a source for the connector.  The cheapest thing
to do is probably just replace both halves of the connector
with something else.

Here's a good place to start reading up on hardtops:

 http://www.miata.net/garage/hardtop/

It shows pictures and part numbers for two different pigtails,
but it doesn't say what the applictions for the pigtails are
(what years cars/tops they fit), so I wouldn't order either one
without further investigation.