Sleeping pad is a tradeoff between size, weight, and comfort. Assuming we are talking non-insulated pads...
Those Thermarest are supposedly great pads, however they are just so noisy that I personally wouldn't use one
I'd recommend looking into these three from most comfortable to lightest and smallest:
-NEMO Astro Air
-Klymit XL Recon
-Klymit X-frame Recon
All three are at least as small as you say. The X-frame is ridiculously small and toted as being used in somewhat significant numbers by CAG. The NEMO Astro Air is really comfortable and has nice thick volume. I looked at these three pads recently in a purchase for myself and ended up with the XL Recon as I valued the ability to use the pad inside the sleeping bag as high (prevents rolling off pad, keeps pressure better, loft pockets seem to work better) and I felt like the X-frame was simply too small. For me, in a combat priority role that pad makes sense, however since I am not in that role, I figured I would benefit from the increased comfort of the XL. Also, the XL has a really nice integrated pillow in the pad. So far I really like mine.