Here’s something you might want to try to strengthen the plastic replacement piece.
Use the methyl Chloride and put just a few drops into the fill area of the print. You don’t need much. Just enough to wet. We found out years ago that methyl Chloride will allow you to bond PLA together quite strongly. It will also bond PLA to Acrylic btw. It should help keep the plastic from cracking at the weak bonds between the lines.
Its not going to dissolve the whole piece unless you leave it in a bath for a very long time. So its not good for smoothing like acetone is for ABS.