Which Radiator Cap?

[Tarmac Tickler]

I need a radiator cap, not for the overflow but the main part of the system.
Not sure what pressure I need to get and where to get the right one from?
My current one doesn't seal properly and I am sure shouldn't be on the car....
Thanks.

[Tarmac Tickler]

Thanks, that looks like a good site, will investigate more tomorrow.
Should have said it is a 2.8 if that makes a difference.