I would be interested in the technology. We do some work along those lines, but typically that frequency is specialized.
Receiver and transmitter designers would be the primary group needed that component. They need to put a small connectorized rejection filter in-line to prevent overloading of the RF front end for a receiver, or place your unit in the output of their transmitter (requires medium to high (200 watt) power handling).
Hence, any company involved with receivers or transmitters. Primarily working for military customers.
You need marketing help and to write a paper and submit it to RF Design, or Microwaves & RF, or other magazines. I read these magazines every week, just to see who's made a new widget.
Give some more spec's without giving away your approach, i.e. rejection bandwidth and depth, VSWR data at distance outside your rejection frequency. Is the rejection bandwidth variable?
Sounds like you are not too savy in the business side of the microwave world. If I were you, I would patent the idea, then contact one of the top microwave filter houses to market and sell your idea (under license).