Gareth, as Robert has already said a clear vinyl won’t really be any good to you as they don’t contain UV stabilizers and the customer has asked for this.
Look in the digital media sections of suppliers cataloges for clear laminate, have they said what they want it for because it might make a difference to them if it is Matt or gloss.
I would also offer them a couple of different options as well because generally speaking the more expensive the laminate the longer lasting it is.
Companies Robert mentioned all sell it along with people like Robert Horne, Victory, Metamark, in fact pretty much anyone who supplies digital print media.