I am a novelist writing fantasy and the world I am writing in uses archaic language (not intense, simply for effect). However, I've been unable to find a reference work that has a list of archaic contractions. Does anyone know a source for such a list?

You have not mentioned the period. B. Groom's The Diction of Poetry from Spenser to Bridges (Toronto, 1955) contains a lot.

Of course, I needn't tell you that the writer should already have that knowledge before he commences his work.
I would suggest going to a web site for Garrison Keillor.

I once saw a list of archaic contractions in a book which had a forward by

Mr. Keillor. Now I can't find it.

My grandmother used every one on the list on a regular basis.