What about using a hop bag? Sanitize it and stuff it in through the PRV being careful to keep the top out. Fill it with pelletized hops through the PRV. Then tie it closed and use a piece of sanitized fishing line to anchor it to the CIP arm or something. The fishing line is thin enough that you'll be able to reattach your PRV and get a good seal.
Weighing down the bag a little bit with some small stainless steel parts isn't a bad idea. They just have to be small enough to fit through the PRV opening and into the bag.
Just a thought.
Head Beer Guy