Why do you think you need a kit for 9VAC ? All you need is the transformer, if you're building it into something.
If you want it ready made, you can buy plug-top AC adaptors from Maplin, although they only do 9V in 500mA. Rapid Electronics have a 9VAC 1A one. You used to be able to buy the plug-top cases empty, into which you could put a transformer, but I don't know if Maplin still sell them, but Rapid Electronics do.