Originally Posted by
FBinNY
You can improve things, but how you do it depends on the headset. On some, you can fit a large rubber band (I use the one that comes on Broccoli) around the lower headset assembly so it closes below the crown races. On others, a disc pressed on below the crown race reduces spray entry, and on some headsets you can trap an O-ring between the crown race and heat tube or bearing skirt.
Either way, you're choice it to improvise a better seal, or drop the fork, and inspect, and grease the lower bearing every 6 months or so.
It sounds like the OP is using an integrated headseat. If so, I think he should be able to replace the lower bearing and crown race with IS-compatible parts from any manufacturer, e.g. a Cane Creek 110 stainless bearing and fork crown race with a sealing gasket around it.
Also, I believe a common trick in the MTB/cyclocross community is to take a section of a large-diameter inner tube and stretch it around the lower fork crown and head tube interface.