Ebay is ur friend really mate, i know there are some polish replica kits, some aint too bad (glass reinforced plastic - GRP) which is a similar material to standard, but you will still need to buy all the runners and guides from SEAT.
I think i priced it all up with a little bit of discount new, at about 900 quid primed. Then you just got paint and fitting.
Ideally you need to find a breaker with one the same colour as yours!!
My wheels are the cupra starfish ones, 17",
Jimski