We made ours when we replaced them as the factory parts were not available. We bought 316SS flat bar (over $400, wholesale. 11 chainplates) but it was not available in exactly the same size as the original plates so we bought the next size up and had a machine shop mill them down ($150) to the correct width. We had to cut them to length, bend an angle into some of them and round the corners and drill the holes (had free access to metal shop), which took quite a bit of time. The stock you buy is not smooth at all, and to get a mirror finish is extremely time consuming so we had that done at a shop as well ($350). The point of this is that even though $1000 sounds high for a few pieces of flat bar, it's probably less than you will have into making them and it will take a LOT less time.
SV Laurie Anne
1988 Brewer 40 Pilothouse