Ok this has been a real educational experience.
The SRT-6 is very difficult to find parts for so after many hours of combing thru parts vendors I have this to offer up.
While MB has pumps available they are a bit off the scale on pricing. but then again thats MB for ya.
However I have come up with the A1 Cardone parts numbers for this pump.
They are as follows.

remanufactured pump: 57-1627
New pump: 57-83333

The remanufactured pumps are not available. seems you have to ship your old pump back for rebuild.
There are numerous places listing the new pump with a 7 day lead time. My assumption is they have to find them in the supply system and route them to your vendor.
the pricing on the new varies from $101 - $200.
Most anyone who sells cardone can get them.

i have included the pic for the cardone unit.