You don't have to spend that much. Buy a one-piece outlet and plate with a built-in GFCI breaker in the outlet. Choose a 15-amp or 20 amp GFCI depending on the surge capacity of the inverter. The outlet will have hot side and a protected side wiring screws. Mount a wiring box for it at the location by the inverter.
15-amp, $12.40 at Home Depot
Wire a cord with a male plug on the hot side of the outlet to get power from the inverter output. Run your other two outlets to the GFCI outlet box using #14 (15-amp) or #12 (20-amp) wires. Connect the black and the white wires to the protected side of the GFCI. Don't be tempted to only connect the black, and wire nut the hot and protected white wires together. The green safety grounds can all be tied together.
Voila! you now have a circuit breaker that protects all three of your outlets, and GFCI, no less.
THANK YOU Redbear!!!
great idea and saves some room due to bulky box!