How to find wireless headphones in a given broadcast frequency

I have a wireless microphone system connected to an amp, speakers, recording equipment, etc, in a lecture hall. A couple of the students have difficulty hearing (even sitting close to the speakers) and we would like to purchase wireless headphones for them to use during the lecture. The microphone is broadcasting at 805.100 MHz (it's written on the box). Is there a good way to find headphones that receive on that frequency? I've googled around and none of the information I can find lists the broadcast frequency of the headphones.

Question by just.another.programmer on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.