To keep my Testor's square jar full, I get methyl ethyl ketone (MEK) by the gallon at my local paint store (which, curiously, is next door to my LHS).  Be sure NOT to get the MEK equivalent thinner -- it is not equivalent!  MEK is also available in quarts.

If you want something a little different try toluene, also at the paint store.  It used to be the main ingredient of Testor's tube cement.  I don't know if it is faster or slower drying than MEK, but you can get a quart of it and experiment.

Finally, if you want something that dries very fast get a gallon of methylene chloride.  You'll have to get that online and it ships as hazmat, but a gallon will last you a lifetime (or a large club for 5 years or so).  Just be very careful cuz methylene chloride is hazardous by inhalation and can cause carbon monoxide poisoning.  Just use with plenty of ventilation.  This is the active ingredient in Tenax 7R and some other cements, including one of the Plastruct cements (I forget which one), Flex-I-File "Plast-I-Weld" and the original MicroWeld (not the current one).  Just be sure to keep it in a glass jar with a teflon seal, cuz it will dissolve just about anything else.

 

I actually prefer chloroform as a solvent cement, but that is getting hard to find, because it is considered a medicine, even though it is less hazardous than the methylene chloride!  It dries slower, but is considered a carcinogen or a possible carcinogen -- something like that.

One last thing.  Although not used for a cement, xylene (or xylol) works great as a thinner for ScaleCoat I paint.  It dries slower than ScaleCoat I thinner (a/k/a lacquer thinner) and gives you a high gloss -- love it!  Thanks to Steve Hoxie for that suggestion.

-- John