I have been ordering strings on Yahoo Japan Auction.
Tsugaru set would cost you about $16CAD.
I have used Zenmarket.jp so I can ship it to Canada and do not need auction registration. Helps to have it translated as well 8-). Shipping prices quite decent and you can combine many purchases in one package to make it cheaper.Plenty of parts for different shamisen sizes as well as accessories. I have been buying bachi, koma, strings and etc as well as damaged shamisens.