The 30-year requirement is going to be a tough nut to crack. It's very difficult to find Cobra replicas in Europe because of import regulations of age. The other factor in that is that it is unlikely that someone is going to find an importable candidate (the window rolls backward), bring it in with all the VAT expenses, and then let it sit so that it's got some additional age that makes it a rebuild candidate again.
That said, there should be plenty of cars available for this kind of project. I've seen some true kits that were not well built and could use some TLC (mostly body work) that would seem to be a good candidate for this kind of project. I'd suggest keeping an eye here in the classified ads and also monitoring
www.cobracountry.com. Places like autotrader.com and ebay also get older kits on occasion. It's not an impossible search, just one that will require a fair amount of patience.
Does it get easier for you if the car comes from Canada?
Good luck!!!