Gooseneck reefers?

Not sure who makes them or if they can be converted to gooseneck?--but check the local beer distributers in your area--the local A/B (BUD)in Orlando--has smaller(drop deck)type reefer trailers they use for specialty stuff to convenance stores--similar to side loader beer/pop trailer--they pull with very light single axle day cabs--this may be a start--or may require you modify the 550 with a fifth wheel--possibly camper type?
Pulled a reefer my entire life--but other than that--I haven't seen anything manufactured like you are describing--of course as with any other specialty item--the answer unfortunately is always$$$$$$--you could convert almost anything--In fact as i am thinking about this--if you have a shop or some creative enterprising people around--I'm betting(depending on temp required) you could pick up a good used utility trailer(ex racer etc)in almost any length/configuration--and convert it--blown insulation--then some kemlite--and a small TK unit--just a thought
Good Luck

 

Put a straight truck cold box from an old or wrecked short truck on a gooseneck trailer

 

http://tulsa.craigslist.org/grd/2265326721.html

 

You are welcome--and all though I know nothing about this personally--I had a buddy awhile back that was hauling campers etc--had 3-4 balls on a receiver hitch--then a 5th wheel on the flat bed part of his F350--with some type of clip in system--where he could--take the fifth wheel off--support system under bed level--and insert ball type for gooseneck--or just leave deck mt--although there was a hole in deck--but that I guess could be covered easily--unfortunately we have lost contact and I know his rig was set up by MARK111 in Fla--who are out of business--but ZI'm thinking maybe a full service camping center might have seen this--or possibly one of the camper driver a away services that does this type of work--could point you in the right direction--so you could go whichever way works best for you!
best wishes in your future endeavor~!

 

Just use an inverted 5th wheel, there kingpins that will drop flush with the bed when not in use.