Try
Cumbernauld .
pooleys
I haven't bought anything from them but I don't know of any other shops around Scotland. I'd ring before turning up to see what they can offer you (the few times I've been there, there didn't appear to be someone manning it). They had a number of headsets on display last time I was there (don't know which one).
(I have no connection to Cumbernauld beyond flying in there a few times)
Edited to add:
There also appears to be one in Inverness at
Highland Aviation