Our insulator retainer acrylic part broke when we hit a blob of plastic. I was able to glue it back together but think it is a good idea to have an extra one around.
OK, the acrylic part just shattered, so I installed the printed part and it is working great!
I was concerned that the insulator may get too hot for an ABS part, but after several hours of operations at 220 degrees, it is working fine.
Be sure to get a firm raft, as it is important that the part prints without warping.
There are two files that are pretty much the same, use either one:
insulator retainer.stl which I made in sketchup from dimension measurements
insulator retainer built from dxf file.stl which I made by importing the dxf file from makerbot into sketchup and then modifying to get the third dimension.
Print out the part and use it as per the plastuder assembly instructions.