Leaking toilet. axa model?

Hi, my customer has a axa toilet with a side entry fill valve. The problem is it's leaking. I have tried rewashering the valve but it's still leaking even though i can see no evidence of any damage to the actual valve. I have looked at screw fix and they do not do ones for this specific toilet. Can you point me in the right direction or give some advice please? Much appreciated. If someone would like to call please do so on 07535597406.

Thanks in advance.