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)
The slab side covered hopper was first built by the CPR in 1946. Eventually, there were over 2,700 cars of this type in service for the CPR, CNR, TH&B, PGE, and CGLX. While the majority of the cars had six hatches, there were also 8, 10, and 12-hatch versions in service. The Gooderham car is available with either 6 or 8 hatches.