I was looking for the Trangia mini pot handle myself a few months ago. I searched high and low, and all the online retailers said they themselves often can't get just the pot handle alone. I think I saw it on Amazon or Ebay, but with shipping to where I live it would have cost almost as much as the whole mini Trangia set.
Vargo has had it before; doesn't look like it's in stock now, but you could email to ask more:
I ordered some Trangia odds and ends from them, and found they had a very reasonable international delivery.