Check with O.P.G.I.. They have a pretty extensive catalog of parts for 67's. Also if you want to buy used part you could try www.bestoffercounts.com , just email him on his sight the parts you need and he will let you know if he has them.
When I did my driver's seat some years ago, I had trouble finding the foam and used Chevelle foam. The GM buckets are basically the same. The problem with the Chevelle foam was that the recess' for the cover tie backs were in the wrong place. I used a die grinder with a carbide bit to make the recess' in the proper places. It worked great! It is quite possible you can get the correct pattern foam now, but in case you can't there is how you can get past it.