Hi there-
I’m looking for a used 12" uni for my young son to learn on.
I’ve got a Semcycle 12-incher that I’d probably let you buy for $30 or so if you were a local buyer. But I’m guessing shipping would be at least that much or more from UT to VT (even though the states are only one letter apart in the post office abbreviations, apparently there’s quite a distance between the two). 
Also, as I recall, the seat has the old rubber-style cover and it’s always coming undone, so it would probably need to be taped on.
UDC sells a 12" Hoppley for $87 that might be a better option.
The wheel needs replaced on my 12" Semcycle and I confirmed that the seat is as I said previously, so it would likely need a better saddle. I think it’s hardly worth the cost of shipping it across the country.
Hopefully someone else can help you out with a 12" that’s in better shape than mine.
Thanks for looking. I have no objection to buying new from UDC, but figured that much like other gear, kids unis might circulate from time to time.