I'm pretty sure the firing pin spring is the same for all the SIGs. I could go to all my parts lists and check it to make sure, but that would require I put down my beer and get out of my chair, which I'm just not willing to do at this point in the evening.
(EDIT: OK, i just looked over on my desk and found a parts compatibility list. The models that share the common firing pin spring are the 220, 225, 226, 228, 229, 239, 245, SP2009 and the SP2340. The part number you want is 34221560. On current packaged parts, SIG will not include the model numbers of pistols that were discontinued at the time they sold and bagged the parts. And you owe me a beer.)