Motorcycle engines have been aircooled for, Oh, about 130 years - if they got too hot, someone would have noticed by now. (The oil in the engine does a bit of the cooling too)
Yes, they will get hotter if sitting in traffic - but being aircooled means the hotter they get, the more heat they lose to the air. If you sit for ages, the petrol will probably vaporise in the carburettor, and the engine will stop. When it cools down, away you go again.
Watercooled cars often can't idle forever either...
Is Irish traffic that bad ?
Can't help with Irish sources - do you have ebay or craigslist or a local equivalent ?