I do carry one and it is from Putnam Hitch Products.
It lists for $209.95, your cost would be $189.95 with $26 shipped to your door.
This item adapts a gooseneck style trailer to kingpin for use with a fifthwheel hitch and is rated for 24,000 pounds. Would need to know if your gooseneck is a round tounge or square and if it is 4" diameter.
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