Look at this bar. The LEDs are in the base and fire into a rotating reflector, similar to the new Vision SLR
http://cgi.ebay.com/ebaymotors/Preco-Clear-Amber-LED-Hybrid-Mini-Bar-Strobe-Light-Bar-_W0QQcmdZViewItemQQhashZitem5197377da6QQitemZ350429347238QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories#ht_4314wt_957
http://cgi.ebay.com/ebaymotors/Preco-Clear-Amber-LED-Hybrid-Mini-Bar-Strobe-Light-Bar-_W0QQcmdZViewItemQQhashZitem5197377da6QQitemZ350429347238QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories#ht_4314wt_957