Look for a bus repair place they will repair them these are the same AC
units that many mini bus' use. Also going price for a 13,500 replacement is
about $550 installed.
It's almost easier to replace it yourself takes about 1/2 hour or so.

Is it central or a simple rooftop, like a camper? If the latter, some RV
places have an association with a local certified AC dealer. The RV joint
dismounts it, the AC subcontractor repairs it, then the RV joint puts it
back. If you're willing, you can do that pretty easily yourself.

If you're not going to do it yourself, you want to make sure whoever's doing
it restores the roof seal properly. Hidden leaks can cause significant
hidden damage.

My Coleman has a Carrier AirV. I've never had to repair it but I believe the
RV dealer has a deal with Carrier, where they simply exchange for rebuilt. I
have no idea what the cost is but it seems like a reasonable arrangement for
an RV dealer that doesn't want to get into AC repairs.