Century probably won't have them - try the shock manufacturers like Fox or RockShox for a good stock of coils. You might also try White Brothers Online Catalog
This wire size and OD are well within the range of modern cold coiling machines, which can coil and cut off up to 3/4" tempered 9254 alloys. Even if furnace atmospheres and temperatures are correct, a coil spring is flexible at red heat and will frequently distort in the furnace. It's easier to...
Hollow wire compression springs have been done occasionally in the past. Ford experimented with them in the 70's. I tinkered with them in the late 90's for mountain bike suspension (that was when mountain bikes cost a lot more). I recall hearing of some high temperature applications where...