Instead of the mylar, would you want to use a regular PC reflector?
AHSupply has the Part 36117 - MIRO 4 Reflector for one 36 watt compact
17.25"L x 4"W x 2"H
Price: $15.99 http://ahsupply.com/mcart/index.cgi?code=3&cat=9
Marine Depot sells a PFO reflector that's similar to the one used with AHSupply's 55w kits. It's 23" long; so it will need to be trimmed. It's $1 cheaper and the shipping may be less too since they are in Anaheim, CA.
23 inch Polished Aluminum Reflector for a single 55 or 65 Watt Bulb
23" L x 3.7" W x 1.4" H
Our Price: $14.99 http://www.marinedepot.com/ps_ViewIt...ct~PF7131.html