WalMart is perfectly willing to sell you (via others) some hose washers online. Pretty cheap, too. I just think it is ironic they don't carry any in the stores, when they have so many garden hoses and so many hose accessories in the stores.
What I should have done, is to take one off one of the hose accessories and tried to buy it at the register. That would have been hilarious. I might just go do that for the lulz.