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.