I googled until my fingers had blisters looking for a HK-4 slip on hood for the 28/1.4 lens. I called all the big houses all across the country and no one had it. Even B&H has it on backorder. Gaye had the same problem and finally had to go to the UK to get hers.
I finally found a place called Adolph Gassers Camera in San Fransisco. They had it for $20. I was just about to give up.