Hi, I am selling these both here and eBay (cheaper via oople)
They are made oversized so allow for many different fixings and then trim down to as small as you need it.
http://www.ebay.co.uk/itm/3317694664...430%26_rdc%3D1
Lots of people ran them at the BWOC at Silverstone over the weekend and nobody reported a damaged or broken one.
Regards Sam