I'll give it a shot.
DIYer or not?
Look in the massive West Marine catalog on paper or website, vendors offer separate evaporator (cold side exchanger) and hosed into compressor/condenser (hot side exchanger main units) for the very purpose of conversion or home make boxes. I believe the boxes are foamed outside (insulated) out of Greenwood (or Greenville I get the two mixed up). (mine all insulated above and below deck), check with Grady HQ. Depending on the unit model selected off catalog, cold plates get bigger as rated higher BTU, it can be ice of less just cold. Contacting the product reps they can assist with figuring out how cold and what unit is recommended, limitations, but will ask about details of box, sun exposure, etc etc.
You have to locate the main unit somewhere (suggest Grady HQ for advise) where access and heat can exhaust. If SW cooled heat exchanger all the better, just like factory AC cabin comfort units. Hoses get routed via boring into box and plugged together, I believe all is pre charged. Photos of the cold plates should be in West cat, check Defender too, etc.
It's a start, well within my DIYer as long as main unit space exist, but will break the $$ bank for me - rather buy ice or elec icemaker juiced off Honda 2KW unit portable already have it for power company "lights out".
Anyway, it's a start for you.
If not a DIYer, all you have to do is contact the product vendor who will provide authorized installers/service/etc, in your area to discuss.
I'd like to do a job like that, I bet it's challenging presuming the ship will be limitated or lacking for space. Just to do it never did before.
