I wouldn't say it'd be too difficult to re-trim, after all, it's a fairly square object with the only curves on it being quite soft-sloping. I don't know how tidy you'd get the underside, but who's going to see it? I'll try to take some piccies of the lid part of mine and post them later, may help you get a better idea?
Also worth noting too that you can of course buy the top-part seperately...
Checking prices now, it looks like a cloth one is £33.14 + VAT and it looks like Alcantara and Leather are the same price, £50.75 + VAT.
Regards,
Rob.