If all else fails you could can butter yourself.
Canning butter 1
Canning butter 2
Genneral canning

As for a stable fat for making pemmican. One of the best is rendered pork fat. AKA lard. Although any rendered animal fat will work.

The trick is that the fat is rendered. In other words cooked. Then the liquid portion [Rendered fat] is saved. It is the solid that that becomes rancid.

I have also read that peanut butter can be substituted for the fat in pemmican. I have not tried it myself so can't vouch for it. But in theory it should work. Maybe not as well or for as long. But it should work. Using peanut butter would increase the level of protein and probably the taste.