I see you are in the Great White North, so I can not comment on local availability, but in the past I have gotten mutton tallow from local butchers. In our modern I want it now world, I have picked up a few pounds from the good folks at Duro-felt, though for you questions are can it be shipped to you with minimal pain, if currently available.
Taking another path, I’ve used rendered lamb fat as a substitute (bride likes lamb chops) with almost as good results as with mutton tallow, at least in my opinion. Unfortunately, the few pounds that I had were purged, even though they were stored in the so-called beer/bait fridge by the previously mentioned bride during a ‘clean up’, so I have limited actual data. My stock of raw lamb fat is building, and unless there is another purge, I may have data on how well the stuff works. Maybe….