The fuel pump relay is in the underhood fuse block. It is energized by the Vehicle Control Module (VCM) by supplying the relays coil B+ and ground is constant. The 20 amp "ECM-B" fuse provides (ORN) to the relays switch contacts with B+ on terminal 87. Terminal 30 is the GRY wire to the fuel pump(s). Find the GRY wire and add a soldered wire w/shrink tubing inside thru grommet to a quality toggle switch to handle 20 amp surge and 7.5 amps continuously. Run second GRY wire back out to OEM pump wire and solder / shrink tube. Should be good to go. Don't place the toggle switch where your knee you hit it going down the road. Use of all GRY wire is you choice, but use wire of same gauge.
Ground from the fuel pumps relay coils would be lower amperage by far, just same process, different wire from same relay.