Unless things have changed since I went all-custom a few years ago, Tikka does not sell standalone firing pin springs.
I learned this when I was having what appeared to be light-primer-strike issues with a .223 T3X Varmint. You might check with Mountain Tactical for any change. The reason I was given is that the firing pin spring in Tikka bolts is far stiffer than most, and at that time apparently Tikka/Beretta had a proprietary tool to facilitate removing it. The gentleman with whom I spoke said they managed to remove a Tikka firing pin spring one time - and wouldn't do it again.
Making a very long story very short, my issue turned out to be a misshapen firing pin - the tip was cylindrical, with no radius, so firing pin force was spread out over a larger area of the primer. Once my local smith fixed that, the problem disappeared. The spring was not the issue (nor was the bogus noise I got from Beretta after they kept the rifle five weeks and sent it back in the same condition as before "servicing.")
Good luck with that. Beretta’s customer service is notoriously bad. I had an issue with a TRG a few years ago, called beretta who told me brownells was the service rep for the states. Brownells told me they couldn’t help and to contact beretta, beretta then told me I was SOL.
OP, try sourcing the parts yourself or reach out to the aftermarket vendors.