My son rides an Aerox 50yq.  We keep going through headlight bulbs and it has been suggested that we have a fault lighting resistor.  I cannot seem to find this part anywhere to purchase?  I am wondering if I buy a complete headlight kit will this come with a new resistor or will I have the same problem with the new headlight set?

Sounds more like a charging fault, have you checked the output from your bike?

Look for the voltage regulator,  [  online manual,]  and renew ,  not headlight,