While reading about this Unimog camper conversion
saw a mention of the AC system.
Sleeping Well 12volt air conditioning.
They bill them as "no-idle" air conditioners but you'll need around four deep-cycle batteries depending on load. They use a Danfoss compressor. There is a through the roof model and three different sized component systems. There are U.S. distributors.
Couldn't find anything in the way of prices.