I used Victory cranks on a bike I rode on and raced on for nearly a decade. They were as stiff if not stiffer than Dura Ace of the same vintage. During this time, I only had one bike, and I logged some serious kms. In all that time, I never needed to change a chainring. This was pre-indexing though, so you might not get the same mileage these days...
My point though is.. that you don't need to have a ready supply of chainrings for your bike to be functional. You will also have plenty of time to look for another one before your current one wears out.
Now, that still doesn't solve the problem of where to get your first one from. Strange sizes do occasionally turn up on Ebay, but if you can't find what you are looking for, you can get one from a specialist manufacturer.
In the UK the best seems to be Highpath Engineering
but my local manufacturer, Underground Cycles
does them for a fraction of the cost: about $50 AUD. Lots of guys around here use these, especially for track racing.
Incedentally, the Highpath Engineering site has a good reference section on drivetrains, and is especially useful for people who want to mix and match Campag and Shimano components of different speeds. I'll leave it to the nerds to post links to these bits in the appropriate places.