interior door mirror blank trim removal

[trev]

You know the ones, the little black triangles of plastic in the front corners of the door windows where the door mirror bolts on and the back corners of the rear door windows.

Is there a way of getting these off without breaking the clips off the inside? I'm missing the two left ones from my B4 estate and I have a whole B4 estate here for breaking that I want to take the trims from. I already broke a pair of them from another B4 estate trying to pry them off.

Without resorting to sorcery or black magic, is there a knack to getting them off neatly and in one piece?

I've run a search of the B3/B4 section to no avail.