Yeah, I think this is your best bet for the time being. I've found that the generic clamp thing I used for my 3G works pretty well for my Eris (can't tell if
this is the exact model or not, but close enough... as long as its adjustable, you should be fine).
Only issue, though: I have to be kind of careful how I place it in the holder; the Eris's volume buttons are placed slightly lower on the body than the iPhone's, so my holder has a tendency to silence my phone inadvertently if I'm not careful.