2005 GEM Master Cylinder

I have a 2005 GEM E2 on which the brake master cylinder has failed. Does anyone know of a automobile cross reference part to use on it? The part designated for the GEM is $150 but I know this has to be a part previously used on a production Chrysler or something. Any help would be highly appreciated.

We have never had a failure on four GEMs, each with many miles. Failures do not seem to be common. There are at least three different units depending on year and model. All prior to 2005 with drum brakes use the same unit. 2005 and later with four lug wheels use a different unit. The elxd truck with five lug wheels uses a different unit. Many o rings are available from industrial suppliers such as Mcmaster-Carr. Through their catalog, I was able to find the caliper seals used on four lug GEMs. To date, the only master cylinder part I have needed was the filler cap, which was matched up at NAPA. My list of alternative parts is below. Anyone knowing of additional alternative parts can post the information, so that I can add it to the list. This list has grown quite long and covers many items.