Malaysian driftwood sinks immediately. It's the only driftwood I've ever used, so I'm not sure about others. Some that would normally float come attached to slate or something to keep them at the bottom. I've never bought driftwood online because it's usually pretty expensive to ship.
I'd say just branch out -- haha no pun intended -- and start looking at LFSs that you wouldn't normally go to -- we make a two hour-long round trip to visit LFS's in VA Beach about twice a month, and every three or four months, make a four-hour round trip to Richmond to visit those LFS's. LOL it's our entertainment.