as long as the wood isnt treated or contain any pollutants anything should be fine, you can attach it to a peice of slate pretty easily if it wont float, otherwise just search about how to soak/boil it.
Boy I am with you on this. Driftwood even from online vendors is outrageous. I bought a piece of african from F&S 12-18" $13.00 It looks like a shoehorn size. and I have been soaking it and boiling it for a week now. My next stop is the nearest river.
Not all woods are safe. And stay away from soft woods as they are almost impossible to make sink and they rot away pretty quick. Also pines, firs, and hemlocks can contain materials harmful to your fish.