Hi,
There is no way or possible easy trick to replace the terminal sealing o-rings without unsoldering the terminals that I know of.
As a cheaper alternative to the Bosch pump there are several possibilities.
One is the Carter p4601HP that produces sufficient pressure and flow.
The carter pump is noticeably louder than a Bosch pump, and some tweaking is required with respect to the mounting/brackets.
There have been various discussions regarding this, a search will give more info on this.
Hans