For the 93 Hummer's the stock replacement blade is the Trico 60-1150, it's a 11 inch wiper blade that is not in most automotive store's stock.  One of the places that I did find who carries it here in Houston, was NAPA Auto parts.

The blade is screwed to the wiper arm as shown in the photos.

But, since 1977, I have been using Rain-X on my windshields and do not use my wiper blades. On the Hummer I have removed my wipers and store them inside the cab, just in case. (And for Texas DOT inspection)

Rain-X will last about one month or so and does not hold up well if you use your wipes. Even using Rain-X, the windshield must be cleaned, wiping the windshield clean with a damp paper towel will almost restore the protective properties of Rain-X to like a fresh application.  Also, if I know there is a chance of it going to rain, while it is dry I will apply a fresh coat of Rain-X.

When I am out of town and I find that I must rent a car and I know there is a chance of rain, I will apply Rain-X to the car. I hate to be driving a car in the rain with the wipers on.  In fact I find that I get a cleaner site of the road then when using wipers. The heavier the rain, the better it works.  But the morning dew is the worst part of using Rain-X, so I try to wipe the windshield with a nice warm damp rag and this helps prevent the dew from forming.
 

• Rain-X does not apply well if the glass is wet or damp.
• Rain-X does not work well if the glass become dirty.
• Rain-X eats wiper blades, or should I say, seem to shorten wiper blades life.
• Rain-X also seem to makes the wipe blades noisy over time. (I think that this is caused by the chemicals within  Rain-X to harden the rubber of the wiper blades).