I believe the primary benefit of a titanium water bottle is that it can serve as a boiling vessel and is lighter than stainless. As aluded to above, you don't want to use the screw cap when boiling, so the material need not be titanium. Add a simple bail made from a stainless fishing leader. If you want, a "boiling" lid can be fashioned out of a small, flat metal (okay, titanium!) disc with slots in it for the bail.

Here is an alternate bail method:

By the way, the REI TiWare Mug should nest nicely over the bottle, too.