One is to find an online seller that has a piece you like that is aquarium safe (depends on the type of wood it is)...
The other option is to DIY a bonsai by getting different sized pieces of driftwood and then siliconing / superglue or screws to bolt pieces together to create the look you want...
I once ordered from a asian site : http://vietaquaticwoods.com
They have a lot of kinds of bonsai with unique shapes, you could take a look if you like to order instead of going on a search of natural driftwood and handmade them.