GFI test/reset buttons are not designed for continuous switching on/off. This could result in premature life or even failure to trip if needed.
No doubt, get a GFI cord or have one in the wall, but don't use it as a switch.
I plan to make a GFI cord from some heavy gauge cable I have, a 2-gang outdoor box on the end, and a GFI and regular outlet. For a switch, I plan to use a remote control outlet
like this. They make a single unit model as well, but get the 2 unit one for future expansion.
With this setup, I can have the pumps plugged in off the back of the stand, away from foot traffic. I also will have a GFI wherever I go to brew. And it will all wrap up nicely with some cable straps for storage/transport.
Another option is the Harbor freight foot pedal switch... Also plug-and-play with extra "cool" factor.