I placed an order from Micro-Mark today. Here's a link to their pigments page. I actually have no idea if this stuff will suit my needs, but I am willing to give it a try.
If you've been following along lately with my urethane tests, you will have noticed that I'm having trouble getting a good shade of red. I'm hoping that a different brand of pigments will be able to get me what I want.
ALSO, of interest, is an item on that page linked to above. There's some stuff sold by micro mark that is billed as a catalyst based TIRE making system. You can make your own tires! I am of course thinking that this might be a great solution for making the soles of the boots. I already have a product ear marked for this task, but I thought it might be worthwhile trying an alternative. Who knows, it might be perfect. And it seems to be formulated to take those pigments I purchased.
Since I'm on a roll, I also emailed the folks at this website, and asked them what I need to do to purchase a few ounces of some of their opaque pigments. I will let you know as soon as I hear back from them.