a smith will IMO charge more for there TIME< than the bolt will costs to buy and replace yourself!
I am pretty sure the size tread on them is below,

Mauser 96, 98 Non-Locking Pack of 2 Trigger Guard Screws Blued Steel
Threaded 1/4"-22

can even order maybe like this, get the longer one and tread more and trim to length you want?
a good machine shop will have for sure? or would think they would or can MAKE for you!

if not here is one, not that costly LOL


and not take them as long
lots of options on places like Ebay to find things
guard screws on Model: 38 SWEDISH, 94 SWEDISH, 96 SWEDISH, all teh same size and treads

https://www.ebay.com/itm/Swedish-Mau...kAAOxylpNTUB3F



or gun parts, they have original rear screws that again can be made to fit?

https://www.gunpartscorp.com/products/14060