Where can i get fireproof insulation for my boiler?

My oil boiler is in a shed(it is made for external buildings).It's not been used for 2 years and the shed is a bit damp.Consequently the boilers extremities have corroded a bit.Ive taken the top off and all the insulation stuff has gone rotten so i pulled it out.The boiler works fine but i need new insulation to go in there as it needs to be protected from frost etc and help keep the heat loss down.As it is inside the boiler it needs to be fireproof too as there is a lot of heat produced when its on.I know the answers of get a professional in, get a new boiler etc so there's no need to reply with that. thank you :-)