For round wound I wouldn't use anything less than a .40-.100 set. If you like higher tension, then D'Addario has a set of .45-.105 XLs that are really punchy. GHS Pressurewounds are really good sounding, but are a little on the floppy side.
I had a set of D'Addario half rounds on my short scale SX Jazz Clone fretless, which sounded really thick and felt just right in the middle tension wise. I am considering putting a set of Chromes on it next.
I try to avoid using .40-.95 sets due to the floopy factor, but SIT makes a set in that gauge in nickel (powerwounds is what I think they are called) that are really great.
GHS and D'Addario make a wide selection of short scale bass strings, and the best place I have found to get them is a
www.bpstrings.com. Bob is really a great fellow, and can get them if he is out quickly, but usually has them in stock.