Of the 3 towns you asked about only Bristol has the information for Property Valuations available on line.
http://www.townofbristolnh.org/Home%...LUES-FINAL.pdf
You will not get the actual property valuation data/card only the amount it is valued at. It is listed by map & lot number not address.
Towns are not required to make property valuations available on line but many do as a convenience to the tonws residents and those who need the information in the course of their business. Realtors & bank appraisers are 2 that come to mind.