IMHO the best source for high-quality, pre-fabricated touchscreen kiosks is Ideum. https://ideum.com/products#kiosk
Ideum can do pretty much anything, as they have pre-fabricated models, custom fabrication capabilities, and an extremely good software team. I can highly recommend them. Unfortunately, that quality is not cheap. There are many companies that deal in lighter-weight, cheaper pre-fabricated kiosks designed primarily for the conference market (Ideum specializes in Museums).
On the cheap and simple DIY side, purchase a touchscreen with built-in player, or tiny external players or micro computers mounted behind. I've done this many times. Cheap and very simple. Monitor, mount, player, all attached to wall or any other surface you can drill into.
Monitors: The major player is ELO touch. I don't love them and not my fav for DIY. Their selection can be overwhelming. I am a fan of Planar Systems 27" multi-touch (https://www.planar.com/products/desktop-touch-screen-monitors/touch-monitors/pct2785/ ). Really pretty screen. Planar does not have a ton of size options, but you can purchase directly and they are good people. Mounts, media players, and microcomputers are all commodities, though Dell Micros are the go-to for museums.
I am more than happy to talk you through all of this. Just give me a call or drop me an email.
Cheers,
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Tod Hopkins
Hoptod LLC
443-472-5978
todhopkins@me.com------------------------------