You had 7 official Championship shirts for every year of the dynasty.
The first was the locker room shirts and caps(self explanatory, stuff the players wore after winning). You can also include the limited runs of Eastern Conference Champs, Central Division Champs, Regular season champs(if you had the best record) and in 96 there was the limited 70-game shirts and 72 game shirts. All stuff players got in the locker room, but it's like a hockey curse, some players wont wear anything except the Conference and NBA Championship shirts. I don't think the 70 win shirts ever went on sale. At least I never saw them outside of a sports report off the evening news. Maybe people at the arena got them? I'm not 100% sure.
The Sports Bar shirts, which were very simple. You could buy them in stores, but they're designed so you could wear a half-apron around them with the printing nice and high. At least that's how a number of others have explained it to me.
The team Caricature shirts.
The Larry O'Brien trophy shirts.
Then you had the back-to-school/fall t-shirts. The league champion was the only one to have it say on their shirts.
The Ring shirts. Some of shirts had the Rings on them, but the Ring shirts were just a picture of the rings.
Finally you had the banner-day shirts. That is what you posted.
Of course, there were a lot of other shirts too, including exclusives with department stores, but these were the basic ones that all 6 championships had. I have A bumper sticker from Venture with Back2Back with a Bulls logo on it. They gave those away for free, and they also had their own official Bulls Tee for 92 that nobody else had. Newspaper Headline, official NBA licensed shirts existed for all 6 as well. But I consider that an exclusive(something you got when subscribing to the newspaper). Sports Illustrated did something like this too, but IIRC, they did more hoodies and sweatshirts.
So there is no real shortage on these shirts, just a lot of holes on documenting all of it for any would be collectors/nostalgics.
My favorite shirts were all fan made, bought at Flea Markets. Those guys did full color prints, detailed artwork, covering a huge amount of the cotton. Very 90s-like stuff, but also very awesome.