do you have an old-school hardware/diy shop near you ? if so they would most likely have stove enamel repair kit, it'll be like a small nailvarnish pot. might have to be done in layers to build up the thickness required.
From ebay.....I have not used this particular product...
http://www.ebay.co.uk/itm/ENAMEL-REPAIR-KIT-FIX-TOUCH-UP-BATH-COOKER-SINK-FRIDGE-/171798276163?pt=LH_DefaultDomain_3&hash=item27fff9a843" onclick="window.open(this.href);return false;