Trials bikes are so small, are you sure you want an 80? Here's a link with some info, pictures of kids on various size trials bikes, and somewhat of an 80/125 comparison:
http://www.thumpertalk.com/topic/578266 ... for-a-kid/Sounds like unless the child is quite small a detuned 125 would be better. If it is small you need, there is a 2008 Gasgas Cadet 80 at a dealer in Albuquerque NM for $2600:
http://www.trialdogmotorsports.com/forsale.htmThese have 19 front and 17 rear wheels and are small.
If you have your head set on an 80 but full size is okay there are 3 Beta 80's for sale at the trialstraining center in Sequatchie TN one 2007 for $2200 and two 2005 for $1900:
http://trialstrainingcenter.com/bikes-for-sale/Also if you need really small there are plenty of Oset electrics as well as the new Gasgas models in 12 and 16" wheel size. Not likely to find anything close to you but the internet is a great [as well as time wasting] tool. Search all the trials dealers and clubs in the country, I'm sure there are more...