I'm not certain where you're located, but in the U.S. witch hazel grows wild all over the eastern half of the country, particularly in the Appalachian states. I know there is at least one species that grows wild all over Europe as well.
In a pinch, you can also source the dried root bark and (sometimes) the twigs as well, online. If I had to guess at the weight of the plant material I extracted, I'd say that it was around a pound, if not slightly over.
There are sellers on eBay and elsewhere offering bark for $25 per pound and up, but hopefully you'll find a place to wildcraft it, making sure that you don't take too much from any one plant, unless it is big enough to support it.
Good luck!
Thanks for the tips! I live in Colorado, USA. I will be looking around for it for sure!
Have a lovely day!
Depending on your hardiness zone, you shouldn't have any trouble sourcing it, and very likely growing it as well. Good luck!