I had the same problem and solved it as follows:
Bought a set of "Stearns" oarlock socket bushings. This nylon socket converts a 5/8" hole to 1/2". I shorthen it to fit the tapered hole.
Bought 2 - 1/2" x 8" "Stanley" steel eye bolts - zinc plated (Home Depot). Cut of the threads and smoothed the edges.
Total cost $10.00 Canadian
