How can I fix my JCB plt25 (M25) petrol strimmer?

Having bought this from a devious, suddenly- disappeared rogue on EBay, I eventually found out that it wouldn't work because it didn't have an air filter and cover. I've spent hours on the Internet trying to find one, but it seems that part isn't available because basically the strimmer is a Chinese copy and nothing to do with JCB.
I've been through all the EBay resolution channels and can't do anything because I paid C.O.D, so although I'd love to go and break all his windows with the strimmer, I really need to find a DIY solution instead.
Can anyone help with some ideas please?

Maggie
July 2013