Ronstan triple cheek block failure; a cautionary tale and request for a source

While putting HONU, (IP38-149) away for hurricane season in Mexico I had one of the Ronstan triple cheek blocks on the cabin top come apart. This block feeds the main sheet, cunningham, and main halyard to the cockpit. The welds on the vertical bolt at the end away from the sheave gave way due, I assume, to crevice corrosion. (see attached photos). None of the corrosion was visible on the surface.I disassembled all the other blocks for the reefing, boom vang, staysail, and main sheet to inspect for hidden damage. I found the aft-most block on the bottom of the boom for the main sheet had a similar problem, the bolt head for the sheave came apart when I tried to remove the nut. The bolt heads on the stainless bolts appear to have been welded on, and the welds have failed. HONU is a 1991 model and I believe these are the original blocks. It would be a good idea for those of you who have similar vintage boats to check the state of the blocks on your boat.

I have found a bolt to repair the main sheet block, but can't find a replacement for the triple cheek block. I plan to call the factory, and maybe Ronstan, tomorrow, but would like to know if any of you have access to or know where I can find a replacement. If at all possible I would prefer to replace the block with an identical, but functional, unit. The large screws that hold the block to the cabin top thread into a backing plate captured between the cabin top and the salon headliner, so drilling new holes would make a mess of both the cabin top and the headliner in the salon.

Thank you,
Mike