Thank you all for all the great links, resources and advice. I was just about to buy a "pacman" version of pizza oven, but fortunately I came across this topic. I thought about either trying to find circle version or searching for a different parts. I found a circle type heater as a replacement part for a regular oven (I attached the image). It's 230V, 2200W with a 205mm diameter.
Do you think that it would be suitable for a modified version of napoli express provided I use a controller to not go up to full power? Also, what's a diameter of your heating element? Judging by the images 20cm should be fine, but if you can measure your parts, it would be awesome. The nice thing about the heating element I've found is that it's already rolled so that 2 circles are powered from one input.
My plan at the moment is to:
* buy one of the g3/optimaelectra/whatever else ovens (there is a optima electra with "pacman" heating element available in Poland: http://jakumammy.pl/
, so this would be the easiest option)
* remove the thermostat
* replace the heating element on top with a 2200W heater I attached
* plug bottom and top heater to separate controllers
* replace all cables with heat resistant ones and hopefully replace all plastic parts with something more durable
* insert a thermometer in order to control the temperature inside
* buy an IR pistol so I don't have to use aluminium foil
* add a reflector like in other mods
* add a deflector?
Have I omitted anything? Does it sound like a good plan? I'm not sure about a deflector. In one of the posts sub mentioned that with higher power it may not be needed. I'm tempted to try a deflector with a refractory stone in order to keep the temperature more stable.
I totally suck at anything related to electronics/electricity, but my father in law is an electrician, so I'll use his help to not screw this up. Is there anything I should pass to him? I mean: anything that may be not obvious?
Btw. the heater element I attached is available at about 15EUR in Poland with various characteristics (all I found are 230V and ranging from 2200W to 2800W). If anyone wants a try I can buy and mail it.