I got 1,200 lbs to work with - can I get a shell?

I think the all aluminum canopies weigh around 300# or you could get a tonneau cover. Not sure what they weigh but I help my neighbor lift his off just because it bulky. I doubt it weighs 100#.

Before you go any farther, even if the 1213lb is real life number - that capacity applies to load with center of gravity close behind truck cabin.
That ain't going to happen with any TC.
Tell us what is your rear axle rating and empty weight on it?

Would you be better off divorcing TC Popups and pulling a light TT?

GAWR is 3,686, scale has rear axle at 1,960.

Now, those are real numbers.
With short camper you can roughly estimate that 90% of its weight will go on rear axle.
Be generous with safety margin.
Just becouse axle has capacity to carry it, doesn't have to make it comfortable.
Than ask me how da heck I managed to add 2300 lb to my camper.

Check out Eureka Campers.

Long bed, short bed, or 5.5' bed?
Shorter the bed, the further back the center of gravity will be. A good assumption is that all the weight is on the rear axle, unless it's a long bed, in which case you may get some on the front axle.
Either way, if you're intent on following the numbers, youll be hard pressed to find a pop up cab over that works. That said, I wouldn't be the least bit worried about putting 1500-2000 lbs in the back with good tires and some air bags/helper springs/Timbrens, etc.
Many of the folks on here will tell you that is totally irresponsible.....meh. If the truck is in good shape, it'll haul that much every day of the week and twice on Sunday with no ill effects.
FWIW, I've driven half tons for years on end with that much weight in them day in day out. That's what happens when you use a truck as a truck. Until the past couple trucks, all of my half ton company trucks would get some rear suspension help first thing and then get used like a truck.
JMO.

I found a 4 wheel camper that I could put on my tacoma based on suggestions here.
bumpy

Bed is 78".

Just took a look at the Outfitter Caribou Lite 6.5. Dry weight 850lbs. Center of gravity 23" from front wall. I think I got something here to work with.

Sounds like a possibility.
The'02 trucks rear springs are probably not what they were 16 years ago when new. After loading the camper the old truck may need some rear suspension help. Lots of aftermarket products to choose from.
Doing the math from actual scale weights makes it easy to find out how much load capacity your truck has..... 3686 minus 1960 = 1700 lbs you'll have to work with before exceeding a tire/wheel or rear spring pack. Those small semi float rear axle on older GMs didn't like to be ran overloaded.
Also you may want to invest in a LT C or D tire to replace those OEM passenger tires.