SMT and 9v battery.....

[momo]

So its great to see all the smt project surfacing these days, it seems awsome to me, but the question is, are there smaller 9v batteries available?, like watch batteries or something like that?
I have a couple of small enclosures that would be great for smt, but a normal 9v battery wont fit.....
I guess they could be made to be powered by external P.S...still, it would be great to find small size 9v to go with smt. Im not trying to reinvent the wheel, but it seems to me that a smaller 9v would be perfect for smt builds.
Cheers