If these are the stock type hubs, your best bet might be Santa Clara Truck Wreckers on Comstock (Lafayette and Central Expwy 408-727-2244) or call Frontier Ford (Stevens Creek at San Tomas 408-241-1800) and see if their parts department still carries them in stock.
Frontier has been trimming down their old parts for the past few years, so they might not have them. But they are a small, inexpensive item after all, so you never know.
You could also try Mission Valley Ford (880 at Brokaw near Montague 408-933-2300). They're trucks only, so might have a few in stock.
One of the better auto parts stores in the area is Winchester Auto (Winchester at Hamilton 408-866-1222) and might be worth a shot too. If whoever answers the phone does not know what you're talking about for some reason, ask for Gary, Craig, Kyle, or Alan.
If you've got aftermarket hubs, try Calabazas RV (Lafayette at Central in Santa Clara 408-982-0859. They're Jeep guys but might have that kind of thing laying around or have a Warn service kit handy.
There's a 4 Wheel Parts store on San Carlos St near downtown San Jose (408-279-4979 and if they don't have a Warn service kit, they can probably get it quickly from Hayward.
If they're not Warn hubs, I don't know who might have the seal locally, but the Warn pieces would likely be identical.
I don't have any laying around or I'd give you some.
As a fall-back, you can always just spread a little silicone around the perimiter of the outer hub and ring, after you've installed them, to seal it off form outside contaminats. That's what I've ended up doing on several Broncos when the seals alone were not enough. That was in those cases where even with a seal, the outer cap was just too loose and wobbly and I wanted some extra piece of mind.
Good luck.
Paul