You can buy heaps of Monty spokes the problem is you can not buy nipples for them as they are an odd thread. The original nipples are alloy and are now stuffed as you have probably found out. later models have steel nipples that rust after all these years.
The original spokes are stainless on almost all models and can be cleaned up but the nipples are made from unobtainium
.
Buchanan, Titmans or any of the wheel spokers can make spoke kits but not nipples for the original spokes. You are much better off get a set through them. I have found Buchanan to be cheaper but Titman makes better spokes (just my experience).