My CAT has ASV finals, and I have a spare, but it's probably too big for the ASV 70. Try Crowe. Not likely that they will have it, but might be able to point you in the right direction. CAT stocks all the parts to rebuild the ASV parts that are on their machines. Can you find out if it crosses?
Loader Parts Source in Elkhart, IN has come through with some hard to find parts for me in the past.