Answer to "I need to replace the pump/motor?"Yes, the pumps are the same. The pump is a basic dc motor with a pump mechanism. You can replace the whole pump or you can also remove the pump mechanism and just use it on the other if the motor is rusted due to water leaking from the solenoid inside.
Answer to "I need to replace the pump/motor?"I got mine from Amazon (http://www.amazon.com/Keurig-Mini-Air-Pump/dp/B00CN0GAKE), it was brand new and I paid $20 with free shipping. Sellers in ebay wanted $12-$14 for a used one. I see the price now in amazon is $30 which it too expensive for a less than dollar motor made in china. If the pump is fine you can probably buy the motor alone from RadioShack and replace it.