So, does it spray off the wheel, and back over the top to spray her? IIRC, the croozer has clear windows on the sides, and it's only the front that has the flyscreen/window?
Or, is it from your rear tyre? You will need a long guard, and probably even a leather/rubber extension on to the base of that, to help prevent it. But, in my experience, the only foolproof way was to put the Croozer's cover down.
If you did want to fit guards, I couldn't really see a way apart from bodge/hacking something thru the cloth body onto the frame - not something I'd advocate. The wheels basically just clip on via their axles into holes in the body/fabric, from memory?