The name for the box you are looking for is a scan converter, they range in price and function. Start at 25 all the way up to 90+ dollars.

The reason you need it: the two signals are total different. tv based signals run at a set frequency that is too low for a normal moniter (also formats, but thats another story....)

if your lcd's have hdmi I would look at this unit by amazon. depending on the number of devices and legnth of cable you might also need a signal amplifier (distributer).

Another way would be to convert the signal to digital media (either film it, rip it, or use one of the many analog conversion services. Once it is digital you can play it from a laptop or media center (I use a old WDTV but I am just a home haunt..... ) just search for a low-midrange media player with the outputs you need on amazon something like this should be fine, You will want to check the manufactures site if you can disable on screen menus....

Personaly I would go digital, then media player / old computors to run it. It gives you more control, you can force them to run of sensors or external controlls a bit easier (arduino ftw).

Something like a portable Kodi server on a Raspberry Pi if you're streaming stick adverse.

This would probably work, just get a drive with files on it and plug it in. Western Digital used to have a nice one but it's sunsetted now.

I chose to go the Roku path for now. I looked at setting up a portable plex server or even using a portable Western Digital media drive, but the logistics are a bit too far for my liking.

If you're looking for a very cost effective solution to just loop some images and or play some HD (1080p and below) H.264 videos, you can't beat this: https://www.amazon.com/Micca-Full-HD-Portable-Digital-Player/dp/B008NO9RRM