Electric heater broken prob thermostat. is it necessary to buy a new one online? or can it be fixed.?

hello. please help. i am in spain. all the shops are shut and no plumbers seem to be working today. my electric boiler keeps shorting out all the elecrticity in the flat. it seems it is the thermostat. is there any online place to buy a new online or do i have to buy a new boiler like the man in the DIY store says?