I think the cap is interchangeable with a ktm... Folks used to use ktm with higher pressure, etc.
Radiator repair places are available that will fix even a very contorted radiator... Just search "motorcycle radiator repair" on google.. A quick search found this one on east coast...
I just tried to fix a hole in my 10 radiator - the guy that did the work said the ktm cap does not fit so confirm this for your model before buying a ktm cap