There's really no good reason to "restore" an SB-40. It's a very nice bass, but unlikely to fetch $500, & that's with original case.
That said, the original bridge looks similar to what's on the XB-400 & others. You should be able to buy such a bass for $200 or less.
If that's not an option, & you absolutely need a "Washburn" bridge, then you'll have to watch eBay & Reverb.com. Washburn has never maintained much in the way of parts, & lessso in recent years.