My husband and I gathered the vines from the woods around our house. Some of the most amazing twists and curves in the vines are way up high (30-50 feet up there) and are very difficult to get to. The vines can actually choke the trees and serve no real purpose, so most places, even parks, are more than willing to let you harvest them.
If there are no wooded areas near you, you may wish to order vines from www.jworlds.com who harvests them in the same manner we did. I've never checked on the prices, but I know that the enclosure we built for less than $300 would have cost about $2500 if we had purchased it from them. They have gorgeous enclosures, though!
Also, remember that any time you bring things in from the outside to make sure they have been de-buggified. Two ways to do this are to make sure they have been in below freezing temperatures for a minimum of 48 hours, or use a bleach/water mixture and spray them generously then rince thoroughly and dry before introducing them to the habitat to avoid any little buggers that might hurt your baby! Good luck!

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Bel 
1:1:1 Green Iguanas
Numerous Great Danes, Cats and Horses
the_elysian_fields_twh@yahoo.com
"Just because you can, doesn't mean you should . . ."