I usually buy from local stores for camping or sports equipment. I´m sure you´ll find some in your area. Globetrotter has a good online shop with fair conditions. I like their customer reviews on gear. I don´t receive money or perks for recommending them.
Foam pads are better for isolating the body from the ground (both heat loss and moisture). Foam pad examples can be found when you follow the link. No name foam pads from the local stores are pretty cheap and durable enough. If you plan to have it in a kit, you should not select selfinflating pads as they should not be stored deflated. A blanket or a sleeping bag would be fine to cover the body. When you have a poncho it can be used to protect a person against rain or snow. The bulk and weight of this gear is obviously too much to be carried all the time. It would be good for a car kit though. I used to have this gear in my car.