Try Funaro & Camerlengo
. They make: P-72 resin kits
. They also make Ping Pong cars. They used to make the MP75 years ago but Steve Funaro dropped the kit since it was a bit of a hack (both sides were the same casting - which is wrong) and it was a kit where the sides, ends and roofs were separate castings (known as a "flat kit"). The P-72 and Ping Pong are one piece bodies (so much easier). BTW if you see Ping pongs on ebay from Images Replicas.. they are F&C kits rebranded.
Note these are "craftsman" kits so a bit of skill is required (not horribly difficult, but certainly not an Athearn Blue Box!) They do make nice models. I'll post a photo of a P-72 I am working on later. BTW hint: to clear the casting flash from the windows: use the BACK of an Exacto knife on the inside of the window to scrape away the flash.
Island Modelworks used to make MP75 resin kits but the mold broke several years ago, and Joe has not redone it. He's also gotten into 3D printed kits (though most are N-gauge). I have one of the MP75 kits and they are (were) a bit "rough". The casting is about 1/8 inch thick so inserting windows is a royal pain. The power train can be adapted from a Proto RDC model. Maybe we can pester him to bring the MP75 back