If you like your Z-Lite, but want a pad that rolls up, try the Therm-A-Rest RidgeRest Solite. Small size is 9 ounces at 48 inches, you could drop a couple ounces with some trimming.
http://www.cascadedesigns.com/therm-a-rest/mattresses/trek-and-travel/ridge-rest-solite/product
Gossamer Gear Thinlight pads are made to roll up. The 3/8″ pad is thicker than you asked for, about 8 ounces at 59 inches, you could drop several ounces with some trimming. Many people love these pads.
http://gossamergear.com/sleeping/thinlight-insulation-pads.html
Lawson carries similar pads, the cosmetic seconds are really cheap, but only available in 1/8″ thickness. Buy one at 24×74 inches and 4.25 ounces, fold it over or cut it up to get 1/4″ thickness where you want it. Or buy two and get creative, they are cheap.
http://lawsonequipment.com/InsuLite-EVA-Foam-Pads/InsuLite-1-8-XL-Foam-Pad-Cosmetic-Seconds-p988.html
Alps Mountaineering makes a lightweight, closed cell pad. But the textured surface probably holds moisture, so maybe not for you.
http://www.alpsmountaineering.com/alps/products/pads/foam-mats/foam-mat
Currently very cheap at REI Outlet.
Stay away from cheap blue foam under many names. It might be “closed cell”, but the manufacturing process creates lots of tiny holes on the surface that hold water. And they are not very cushy.
HTH.
— Rex