Wireless monitor setup - recommendations?

Hi,

I'm shooting some content at the moment where I need to be off set monitoring wireless, I was wondering if anyone can recommend a small wireless monitoring setup which is not overly expensive (if such a thing exists). I only need a 5"-7" monitor, but it would be good if it could all be battery powerable (monitor and transmitter/receiver) Doesn't have to work over crazy distances, just into a neighbouring room etc..

The camera is outputting HDMI only.

Thanks for any help, very much appreciated!