heres a link for some back packs
http://www.underarmour.com/shop/us/en/mens/sports/snow-sports/accessories/bags/backpacks
just be careful what you put in there because it won't feel to pleasant if you fall hard and land on the backpack with hard, sharp etc. things in it. If you go snowboarding a lot consider a locker right at the mountain. Its a lot easier than lugging everything with you every time and if you have to come down for any reason you can lock your stuff up where its safe instead of leaving it in the open where it can get stolen. The season lockers sell out fast so watch for when they go on sale in the spring and as soon as they go on sale buy one. The longer you wait the less chance you have of getting one since they're first come first serve.