The production totals shown in "The Definitive Firebird and Trans Am Guide 1967-1969" by Rocky Rotella are the best I have seen. I don't see that combination in the book. There were 11,649 1969 converts built (13.3% of the total '69s) and 28,091 '69s equipped with AC (32% of all '69s). Using an imprecise SWAG would be 3,500 (13.3% X 32% X 89,700). On one hand you might say a convert top would be imply no desire/need for AC. On the other, it may be that people who would spend the additional money for the convertible option might also be inclined to also add the AC upgrade.
Note that with the uninsulated thin black convertible top in the sun coupled with the engine and exhaust heat below, (plus the hot water always flowing through the heater core in '68; I believed fixed with a valve in '69), the AC was the most disappointing and dysfunctional option on my '68 convert over my daily driver years. Even after being serviced and operating at specs, once the interior was hot from sitting out and the sun beating down, it would never get really cool and comfortable. Pulling out of the dark garage in the morning or driving at night it would be OK.
After purchasing the car we started a restoration. The " nitwit " that owned the car spay painted the interior to changed the color. He toss all the AC components including the duct work under the dash because he was going to race it. We also had to have the engine rebuilt because of a cracked cylinder, using NOS we suspect. The other thing the nitwit did was to drill holes be hind the passenger seat. Before the restoration and after driving in the rain the floor behind the passenger seat was wet . We ripped up the carpet and found the holes. And more holes along the floor pans to above the rocker. After removing the rear seat and panel we found the cause for the leak, a hole in the fender-wall. The tire was kicking up water into the interior. I have always wonder how many classic cars were damaged becaue of nitwits like him
Your right about the AC then again we are definitively spoiled with the AC in modern cars.
Get yourself a "Vintage Air system " The support is great. The system is a snap to install, with the hardest part being pulling the passenger fender to remove the old blower housing. If Nitwit did that for you,your home free. The system blows so cold my wife asked me to turn it down on more than one occasion. How many times have you heard anyone saying the AC was too cold in a Bird ?