Geoff Gooderham resin car kits used to be sold through Central Hobbies (Vancouver). However, that store has closed, so the only way to get them now is to contact Geoff directly (by way of his "Angus Shops" alias on The Railwire)
Note that the photograph above is just a stand-in and not the actual Gooderham model (although it is a Dominion stock car). If you have a picture of the real thing, do please send it to me.
Beginning in 1919 Canadian Pacific began to convert some of their steel frame box cars to stock car service. This simply involved the removal of alternate boards on each side and the fitting of specialty constructed stock car service side doors. In the early 1930s some of the steel frame box cars and stock cars were fitted with more modern trucks and AB hand brakes. Many however remained in service with their arch bar trucks and K type hand brakes well into the 1950s. By that time such cars would be restricted to domestic service only, assigned to the service car roster, sold to other railways or scrapped.