Be careful with tie-down kits, it's not worth scrimping on cheap imitations.
After suffering a very expensive wing repair on my F172 following an unusually stormy night, I purchased what is advertised as the only Lloyds approved tie-down travel kit for light aircraft. Rather more expensive than the ones in certain aircraft catalogues, but far cheaper then a new wing.
You can buy these from retailers but I went straight to the manufacture. Really helpful people and they can tailor an order to your particular aircraft needs.
http://www.spyra-base.com/