another suggestion would be to check your local craigslist for a cheap deal on a red, yellow, or blue hon classic - it is one of the most easily obtainable folding bikes on the secondary market and i am reasonably sure the latch assembly parts spacings are identical on both the stainless and painted models (you'll know when you see it). you can pick one up for around 100usd. take the latch assembly off and keep the rest as a parts bike; it will be cheaper than having custom part fabricated and plus you'll have a bunch of spares.
aslo, note there are variations in the assembly design: