The first problem you'll have is that the Pedestrian Protection System is only fitted to European-spec vehicles and not US-spec, so there's not a huge amount of information floating around for it as I think most users of this forum are based in the US (though there's a fair few Brits on here too, of which I'm technically one despite living in the US).

You can replace the bonnet airbags with resistors, and this will stop the airbags deploying accidentally (or at all), which is definitely a problem that's plagued people. The problem with this is that it won't stop a faulty sensor throwing up a code, and really the only way to fix this is to replace the sensors. Also, as they're accelerometers they give a constantly changing output and if the ECU doesn't see this output change it will mark the sensor as faulty, so you can't replace the sensor with a fixed resistor or similar. If you've swapped the sensor enough that you're pretty sure that you've put a good one in there and are still seeing the errors, then I'd be considering other possibilities such as damage in the wiring to the sensor.

I've attached the wiring diagram for the protection system - you can see that there's a few connectors with a potential for damage - C1PR02, which is the connector on the sensor itself, but also C11-E which is the connector which joins the front bumper to the main vehicle harness, on the left side of the front bumper, as well as C2RP03B, which is the connector on the passenger protection module. I'd be using a multimeter testing the wiring between all these connectors to find if there's any breaks or short circuits as a result of the accident (or even not, e.g. a bad connection on the bumper connector). Let me know if you need more help here.

One more thought - it's possible you need to drive the car for a certain amount of time and possibly at a variation of speeds before it considers the sensor to be good and clears the error.