If you check the post - 'Air-jetting', you will see that there are some pictures for running garden hoses from your air box to exit just under your handle bars. This may give you an idea of keeping water out also. It will cost you about $6.00 at the hardware store (providing you have a garden hose that you can cut up). As long as my handle bars and gas tank don't go under water I run pretty dry.
Do a search for "air-jetting"

 

I have mine snorkled and still have room for a box on the front. also I have worked on a punchlist of some of the other things you can do to your cat.

Water and Mud Riding Punch List (Edit 10/12/07)
Silicone the 4 Wheel Drive Actuator.
Use dielectric grease on all electrical connectors.
Replace the fan fuse with a Circuit Breaker. (Bussmann BUS CB21215 Type II or BUS CB21115 Type I, Thanks Sanny)
Replace the main fuse with a Circuit Breaker (Bussmann BUS CB21130 Type I, Thanks Sanny)
Install fan cut off switch, to turn off fan when making water crossings.
The top of each differential has accordion bladder on them from factory, you can add additional bladder or vent it with a hose.
Install a one way check valve in the carb drain hose (HELP 47149 - UPC 37495 47149).
The battery is vented low but can be left as is.
The radiator can be vented into a Coolant Overflow Bottle (AC Part# 0413-086 with a Stopper (AC Part# 0413-087)
Add a aftermarket fuel filter, this will keep mud and other debris out of your engine.
Permanently mount cable or tow rope from receiver hitch to rear rack to use as an anchor point.
Line your inner fenders with silicone(or cooking spray) to prevent mud fron sticking.
Check diff. fluid after every ride.