You know what's funny to me about the OP's question? Back in July 2007 I was also shopping on the Internet for supportive underwear, but nothing constricting that would pinch or chafe. I came across this one website that included customer reviews of underwear. I found this one pair that seemed to be what I was looking for, and the customer reviews supported that impression. One reviewer wrote that he had heard about the style from lpsg.org and that after buying a pair himself he was very please.
"What's lpsg.org?" I wondered to myself. So I looked.
Large Penis Support Group
When I finished laughing, I couldn't help but to look around a bit, and quickly discovered that there were several threads on interest to me. So, to my surprise, I ended up joining the site, and writing a couple of replies to some interesting threads. I got so distracted, I never did get back to my underwear shopping, but I've been coming to lpsg almost every day for over a year now.
doctorweredying, you said you would prefer not to order underwear online. Do you have a Target near you? If so, I like their Merona line of underwear and C9 by Champion. They are made out of a very thin, light, soft cotton, similar to the fabric used for Calvin Klein underwear. They probably can't compete against some of the more high-end brands other posters have mentioned, but they're cheaper and easier to obtain. If you like them, great. I you don't, you're only out about $10 and can then move on to some of the higher-end brands.
These have a nice pouch and show off your bulge really well. (This model must be a eunuch. Maybe I'll take a pic of myself wearing them so that you can see what they look like on a real man.)
Merona® Cotton/Lycra Boxer Briefs 2-pk. : Target
Because these are long, they don't ride up as much and don't pinch or chafe in the groin.
C9 by Champion® Cotton Boxer Briefs 2-pk. : Target