I just bought some from the Great American Spice Company.  If you use the code BETTER15 before 6/17 you get a 15% discount.  May be enough to almost cover the shipping costs depending on how much you buy.  I previously bought blue cheese powder, charcoal powder, and hickory powder from them.  They have some interesting spices/powders.

I'm not sure where I got it, but a while back I bought Worcestershire powder.

I searched the whole site and could not find bacon powder. edit: found it doing google search.

I'm not sure where I got it, but a while back I bought Worcestershire powder.

I've used that in a rub before at one point.  I still have some in the pantry too.

I'm not sure where I got it, but a while back I bought Worcestershire powder.

I got a jar of that also and used it in jerky, but it turned into a solid brick within a few months. I may try to grind it up and put some desiccant packs into the jar.

For my rubs/powders that tend to cake, such as Tatonka Dust, I store them in a vacuum bag.