Check out Klymit air pads. I have a couple of the uninsulated ones. They're very light weight and easy to use. I've never had an air leak with one.
They have a couple good insulated ones that I haven't got yet since I have another older insulated one. I've heard that they're pretty good. The best one (and most expensive) is called the Insulated Static V Luxe SL. It's 3.5" thick with an R value of 6. It's a little heavier than the less insulated ones at about 2lb.
That’s the one I have. I said Kelty but definitely a Klymit. I like it a lot, so far. Coupled with a closed cell pad underneath, I don’t think any side sleeper will have trouble.
