There are four main places such contracts can be found
(a) post 1702 if involving property then in Deeds - some of the old Deeds go back prior to 1702 and would seem to have been deposited to confirm later transfers - I have all these and no such contract there.
(b) in Wills - generally accepted as will of one or more of parents - check BL's index
(c) Lib Canc - voluntary deposits pre 1702 for safe keeping - most parishes, but not Patrick, have a list of such entries noted in the deed index book
(d) Lib vas - bound in with land transfers though not a general rule - many transfers note that by virtue of a contract bargain confirmed by the officers the actual contract is not included - I've seen several statements that such contracts had been lost etc or in one case destroyed.

I've only just started on lib vas pre 1702 for Patrick (that for Kk Michael from 1656 is now complete on CD with 1627 to 1655 underway + those for Ballaugh reasonably complete)