You could bring it to a repair shop where they will probably install a new power cord. The now-shortened power cord can be fitted with a new plug, and used as before instead - for a fraction of the cost.
From what I can tell, the pressure washer is a 120 volt type. Purchase a replacement plug - called a "cord cap". The most common configuration is pictured below:
A 15 amp / 125 volt male cord cap made by Leviton.
Your's is likely rated at 125V/ 15A (like the one above). This means there's 2 parallel blades and a ground pin - like most grounded plugs in your home. If unsure, bring the cut off section of the power cord to a hardware store to select an identical cord cap. You'll want to purchase the type of cord cap that has terminal screws - not the type without screws. The packaging of the cord cap will indicate how much of the cord jacket and individual wire insulation to remove. A little more or less won't make it impossible to do - but don't deviate too much from these dimensions for the best results. Once the cord has been stripped correctly - Disassemble the cord cap body from the outer shell by removing the screws on the front. Loosen or remove the 2 screws at the cord grip end and slip the shell over the end of the power cord.
Bring the cord cap body to the cord. The body will have 3 screws. One each silver (or light colored), bronze (or dark colored) and green. Loosen all the screws - do not completely remove them. Twist all the strands of each wire so that they are bundled together and there are no stray wires sticking out. Do this for each white, black and green wires. The black wire will connect to the bronze colored screw, the white wire to the silver screw and the green to the green colored screw. You can either insert the stripped wires into the small holes at the back of the terminal screws, or wrap them around the screw terminals themselves. The best way is to wire from the back - but if you choose to wrap around the screws, be sure all the small wires are under the screw head. Tighten the screws and tug the wires one at a time to make sure they are held firmly in place.
Once satisfied that the wires are connected correctly and tight - slide the outer shell towards the cord cap body. Align the screws with the holes in the outer shell. The parts will only fit together one way - so don't try to force it together. Tighten the screws in the front and then install / tighten the screws at the cord end to grip the cord. This clamp should be firm - but not to the point of crushing the cord. Test in a ground fault protected outlet and you're done!
I hope this helps.. please rate this reply - thanks!