Congrats on your new Treos! In terms of flip-lid, most I've seen are of the leather variety. You could go in the direction of a
pouch type case. These are often available in something other than leather - neoprene. We don't sell them in the Everything Treo Store, but Crumpler makes very cool cases. Last I checked, Palm sold these. If not, there are a few retailers on eBay who sell Crumpler. I own two of their bags (camera/laptop) and swear by them.
-Chris