Team, If you are referring to a gas back boiler unit, the chances are that it is manufactured by " Baxi ". If this is the case, you can obtain replacement fire fronts if the boiler is less than approximately 20 years old. ( a good guide is, if the fire front has only 3 radiants, you can't replace. If it has 5 radiants, you can ).
Go onto Google , input boiler fire fronts for a list of stockists. Don't forget , have a Corgi registered engineer carry out the replacement ( he will probably advise you regarding your choice of replacement too )
Hope this helps.