You can order it here, it's a dutch site from my lhs. This is a shop from which i know certain that has the tires in stock
If you race in the rain you will use the kisslings in heavy rain, puddles on the track.
When the track is damp i use Dunlop raintires, or just electro slicks works really good if the track is drying, and you will not immediately destroy them.
And make something to protect your airfilter from the water.
There are a hole bunch of tricks to make the car perform in the rain, if you like to know more just ask.