This guy has done some research in that area: http://www.vinland.com/blog/?p=68

It is the methylene-chloride (dichloromethane) in the Weld#5 mix that does the trick. In labs we use it to dissolve PLA. Chloroform (trichloromethane) will also work.

They are both nasty stuff however, like all solvents that will dissolve PLA. See: https://www.sciencelab.com/msds.php?msdsId=9926060 and https://www.sciencelab.com/msds.php?msdsId=9927133

IF you want to go that way, use disposable gloves, don't get it on your skin, don't inhale the fumes. Do it outside and please dispose of the used solvent in a responsible way. If you know someone who has access to a proper lab, ask him/her to help.