Yes a trailer shop for centre bolts or even just turn your own up if you have access to a lathe. As for the clamps they are easy enough to make and I think they are riveted on, so get some "black" rivets from an engineering shop. Ideally the clamps should have been heated to straighten them to avoid them fracturing. Places that repair agricultural machinery like vineyard cutter bars, etc. are bound to have them. If you have trouble getting them let me know as I can get some here for you.
Cheers, Mick.

