Thank you Fraser.
He already have one, that's why he asked me this.
I always buy thermal cameras with "direct" video output, no matter it's analog or HDMI or what ever.
He just want to view it without a PC or sticking his eye to the tiny viewfinder. (And Wifi streaming isn't an option because no one like to click on a stupidphone in the field)
I found several "UVC to HDMI converter" products, but most of them are Chinese made, I'm sure he won't use them. But this is a good direction to go, maybe I should dig deeper and just find him a good quality signal converter.
Thank you again for your good answer!