Chicago Albumen Works produces POP in the states. We (Camera/Arts, a small
retail store in Sacramento) carry their Centennial POP in both RC and Fiber
Base and their kit which includes gold toner and fixer.
The only chemical processing required is a standard b&w fixer. Permanence and
image color is affected by the common practice of toning with a gold chloride
based toner.
I've done just a little bit of work on POP but quite like it.
Have fun, John
Camera/Arts (the retail store)