We use a skin from JConcepts. I just drew around the chassis and cut out. It's slightly thicker than most skins and works well. Link below, but unfortunately out of stock.
http://www.dms-racing.com/index.php?...ategory_id=512
Another option could be the AE version, link below. I've not used this one and you may need to check measurements first if it will fit, but same principle.
http://www.rccarshop.co.uk/index.php...ive-sheet.html
Cheers,
Jase