I would suggest a pair of locking bolts...the split ones and a spare spring for those. That would be the parts that are actually on the barrel lug that lock up the barrel to the frame.
By the way if you are going to change your own hammer spring on a Contender...not a G2.....you will find it far easier if you have or make up a slave pin. It will hold the spring and hammer together while you are putting them in the frame.