How can i fix a broken knob on my Creda gas hob ?

We purchased a dark green Creda Colonial oven and matching gas hob a number of years back. I have searched through the instruction manual to try and find a model number but there isnt one. Can I get a replacement knob for the gas hob anywhere. On the inside of the broken knob there are three letters 'ITR' and at the bottom 4 numbers '3 423'. 4Creda spares cant seem to cope without a model number.