Sliding side window seals

[ryan6767]

Hi,

I have sliding windows in my van that are leaking. They are the "small sliding window inside a bigger window" type! (See pic 1)

There is a hole through the window at the end of the runner, presumably to let water out. However, the water is just pouring in through this and going off the end of the runner into the van. (See pic 2)
Should there be some kind of stopper at the end to stop this from happening?
I can't seem to find these windows anywhere so I can reference them.

The window on the other side seems to have a different system as there are slots through to the outside rather than a hole. That side doesn't have a seal on the sliding portion of the window itself though.
So I would also like to find another one of these (see fluffy bit on pic 3).

Hope someone can help! thanks