We just installed our keyed thumb locks on the three storage compartment doors. Good service from Bill at Wholesale4inc. We called and spoke directly to him and he knew right away what we were looking for, three locks, keyed alike, a-frame trailer. 503-238-8605 The price has gone up since I found the posting here, and still steep shipping, but they came in three days.
What was difficult was that there were no instructions and the illustration on the package was half worn off. And my DH, though he has installed locks before, couldn't figure it out, so I called Bill and he directed me to the instructions on their website. So here is the link for anyone who wants to avoid the maze of finding the instructions!