The Hostel Shop is a good place to buy outdoor gear, because M.E.C. does not stock every brand of equipment. They also have mail-order. As far as clothing goes, you would do well to not spend tons of cash on nice new pants, shirts etc. Mark's Work Wearhouse sells quality stuff like pants, socks and pile outerwear for reasonable prices. You would do well to buy cheap work clothes, because your clothes will get dirty, abused, etc., out in the bush.
Some companies supply planting gear.
You should check and see how much they charge, and if they do, whether or not you get to keep the supplied gear at the end of the season. Bushpro no longer has a retail store, so you have to visit Neville Crosby, the Bushpro dealer. For those arriving in Vancouver before the season begins, NCI is great place to shop because it's a five-minute walk from the bus station. In Prince George, there is a store called Center City Surplus , which is right downtown, within walking distance of the Netchako Hotel and P.G. Hotel. Sorry, I don't have the number.