1996 Plymouth Voyager Brake Leak

A few years back, I must of ran over something and the main brake line module under the driver side(what is this brake line splitter called) started leaking. I had a mechanic look at it and he slowed the leak down for one of the only lines that leaked. For about 2 years I kept adding fluid, and then I parked it. Since I have gotten it back on the road it started leaking real fast. I have taken it to another more relaibe mechanic and he said replace the unit, but it is hard to get one for a good price.

Please tell me what it is called and how to get a used one on the internet. Are they most likely the same for most models Dodge, Plymouth, different engine types, or do they have several of them and I need to match up the exact part number?

Thanks,