you might be able to make one from a hacksaw blade. They seem to return to a weak spring temper if you heat them and bend them to shape and let them cool. Basically grind the blade to width including fitting the little blade that is inletted into the lock plate and use needle nose pliers to create an eye. Fairly hard to find a blank spring that will fit unless the lock is a production lock. They can also be forged out of 5/16" drill rod and then tempered but that would require a fair good source of heat plus a lead pot to draw the temper with
cheers mooncoon