Anyone know the best place to get some?

There are a few places sell them on ebay. Or you could get your own powder coated/painted. That would be cheaper.

you could always swop with someone who has bought a blackline

200 - 250 ish would get your set re-painted in whatever colour you wanted.

or: http://www.theskodashop.co.uk/product/18%22_Black_Neptune_Alloy_Wheel_-_Octavia_VRS_09%3E12_1Z0071498A

I wish to keep the original ones so would prefer a new set. Then could put the originals back on.

I bought one for my blackline and it works out at 160 per corner at this site http://www.theskodashop.co.uk/ might get discount for four. Its the cheapest ive found and I did lods of looking.