I decided to go the DIY route. Here's an update on how it turned out...

Never was able to find SS nuts & bolts in this size anywhere local: not big box, not little box and not fastener stores. Ended up ordering them all online and they turned out great. Cost about $30 shipped. Grabbed a couple of rubber washers and tube of anti-seize at Lowes, and made the vinyl (plastic) washers myself from a plastic cutting sheet.

Spray painted the iron base & spring assembly with 2 coats of Rustoleum rusty metal primer, then 2 coats of Rustoleum Marine topside paint. Repaired a two-inch chip in the board side with bondo automotive body filler. Painted the whole board (top only) with 3 coats of the Marine paint, with light sanding between coats on all.

The hardest thing to find was the 2 small plastic bolt covers that sit on top. It took 3 weeks for them to ship & arrive, at a pricey $25 or so for 2 pieces of plastic. Couldn't find them anywhere else outside the kit I mentioned in the original post.

I spent less than $100 on the whole job and it turned out great, considering it would've cost well over $1k to replace the board & spring, much less installation.

Pics here.