Is there such a thing for Airheads, Oilheads, or K's?
On a Brit Bike forum, there is a general section essentially called "parts from other non-Triumph bikes that works with this Triumph-specific model". For example, certain brands of oil filters that fit a Japanese bike will fit on certain Triumphs. Same thing is true for various foot pegs, and so on. The list is actually quite comprehensive.