Soller Composite is a very good source. That is where I get my Carbon Fiber from. My only comment is that depending on the color you buy and the type of PR you use there might be some slight color bleed into the PR. I had this issue (which is arguably an issue) with the gray/green blank you see above. Jon Soller, the owner, had me send some of the PR I was using to him so he could do some tests. He discovered the same thing but considered it a non issue because of the small volume I purchase, the application I am using it for, and the very slight amount of bleeding present. I have other colors but have not had time to cast them to see if I get any color bleeding.
I use resin from mrfiberglass.
Joseph