Over the different seasons, Bear switches brands and models of backpacks often. While he's now using his own "BearPac" line of backpacks by CragHopper (Pictures above, available in the UK only), he's used Northface, Osprey, CragHopper, Gregory, BackCountry and other brands before. This post lists all known backpacks or if they aren't manufactured any longer, their closest equivalent.
Here are the backpacks used in Season 1:
Gregory Targhee:
BackCountry Stash BC:
Gregory z25:
BackCountry Stash:
