Try a search - this has been on here before. Not too often, but "before".
Maybe search older than last 12 months.
A Google search will also yield other forums with info.
The various commercial dollys (that are capable) are very expensive, as you may have already seen. Others, like the "Parkit 360" may *not* be capable of moving 5th wheel trailers except on completely flat ground.
If you have a tractor, you are fortunate! - (IMO) look into options to use it.
I don't have that option - and after lots (and lots) of research, the most cost
effective (least expensive and most "capable") way to move a 5th is with a used fork lift.
Most dealers and service facilities use a fork lift with a 5th wheel pin attachment (receiver plate)on the forks.
The attachment is either "self-fabricated" (cheap!) - or, there are commercial ones available for around $200-$300.
Check Craigslist for used forklifts -and- the attachments.
Note: You *don't* want the 'small wheel' fork lifts normally used inside warehouses, etc..
Good luck finding the right "mover"!.. :C
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