Those of you who are scared to death of going into a medical store and buying diapers, I have only one word of advice: Practice.
The more you buy them, the less nervous you get. I bought mine today in broad daylight with someone waiting in line behind me. I wasn't nearly as nervous as my first time, at 10:00 at night, no one in the store but the cashier, and she was a hot blond chick.
I also bought two packs of baby diapers at different stores, to compare them. Baby dry 6 and Cruisers 7. No one gave me a second look, or cared.
So, if you want diapers, just go buy them! Everyone's LAST suspicion is you, they are more likely to think its for one of your older family members. Also, for that extra 'errand' look, take a piece of paper with several items scribbled on it, and look at it often if you suspect someone is wondering why you are buying.