Before going to all the trouble of locating a bolt, which is near impossible, I`d take a real good look at the sear and trigger group first. It`s not an uncommon problem in the early production Model 80 series.
And if it comes down to a new bolt, there are two different bolts for that rifle, early and late production that are not interchangeable. A replacement would need the headspace reset too.
I think I sold the last complete late production bolt available about a year ago on this forum, from listing time to selling was less than 5 min.