The Axim does come with a slim case - slides in from the top. I really like that case, but it's too small for the extended battery (ok, you can cram it in) and there's no way to carry extra stuff (memory cards, etc.).
There are one or two after-market flip covers available, as well.
I don't carry this kind of stuff in my pockets. They're too full of pens, pencils, knives (ok, just one knife), keys, etc.
I long ago gave up worrying about super nerd status. Although I usually don't walk around with stuff hanging off my belt, if it's the best approach at the time I go for it. I won't carry my phone in my (pants) pocket, for example - it hangs off the belt (but I was also one of the last people in the world, it seems, to get a cell phone).
Now, if I were really going for super nerd status, I'd dig up the old case for my TI-30 calculator (the original LED one). As far as I know, this blue imitation denim vinyl case was the first modern, high tech indicator of nerd status.
If I want to really go retro-nerd (pre 70s), I have at least one belt-loop-equipped slide rule case.
And, when I want to be photography geek, I carry my gear using a belt-mount system from
Kinesis. My belt looks something like
this one but I also have a Nalgene water bottle hanging from it. And if I'm feeling paranoid, I also have "suspenders" that help hold it up (only in case of emergency, the belt does a great job of distributing weight on the hips). The Grinder Gear case for the PDA would fit in perfectly with this. By the way, if anyone else is carrying around a lot of camera gear, the Kinesis stuff is really good (although a bit expensive).