PP = polypropelene, HDPE = High density polyethylene. Both are FDA rated for food. Most plasticware will be made out of one or the other. Just include those in your search terms. A hardware store should have a bucket you can use that is specifically labeled as being HDPE, if you need a larger container.
Edit: The cambros are probably polycarbonate, so check if that's safe first. I would use a tool, not your hand; lye is nasty. A plastic spoon would be better.