In the not too distant past I have got them direct from Savage USA, also from Grech Outdoors in Ont. They are the Canadian warranty centre for Savage.
http://www.grechoutdoors.ca/
Grech worked out a little cheaper last time If I remember correctly.You may have to stipulate which style of grooves on the nut, having a Model # for your rifle will help, small shank or large, round or square bottomed grooves.
Your barrel nut wrench should do either style of groove. The smooth nuts are a real pain to torque, even with the correct nut wrench.