Drive south until you cross the border (if you can) then go to any gunstore, pawn shop and some hardware stores. Their, you will find all the Surplus 7.62x51 and bulk .308 you can imagine...
Wait, you said IN Canada, oh, well your SOL on that one. Unless NRCAN approves the metric Sh*t ton of Surplus Several of the dealers above have off shore, their is no cheap 7.62x51 or .308 in Canada.