tweeter adaptor rings?

[DeWitt Harrison]

My '88 5kcs has the Audi 10-speaker system. There is a 'high frequency'
speaker in each of the four doors. I intend to replace these with tweeters
which mount in smaller holes than the originals. Has anyone come
across a good solution, perhaps in the form of a trim ring to convert
from the stock opening (about 2.5") down to around 1 3/4" or so?
I've been surfing around and have yet to hit on a source for a ring
of that kind.

Has anyone come across a 'make your own mold' sort of kit
that could be used to duplicate the outer shape of the stock
speaker that could be used as a starting point to make my
own adapter rings?

Thanks for any ideas.

DeWitt Harrison