Harbor Freight carrys some pretty cheap ones, they appear to be big enough for handguns only and no idea on the quality. This is the biggest one they have.
http://www.harborfreight.com/cpi/cta...emnumber=91957
When you get to about 12" inside tank length they seem to run about $400, like this one
http://www.sonicsonline.com/personal...-cleaning.html
The ones I saw designed for long guns were very expensive.
http://www.sonicsonline.com/f636ht.html