You may also want to consider a new device. I swear by my Treo 650 when I'm out and about. Since it uses a full-featured style browser (Blazer) you aren't limited to WAP only sites.
Not all websites are "mobile friendly" even on a Treo, but you can "test drive" one in your local cell phone store to check for a mission-critical app like this one, I'm sure.
And, it's not much bigger than a standard cell phone. The Treo 650 puts a lot of power in a tiny package -- it gives you the ability to email, surf the web, place calls, stay in touch, check your calendar, jot some notes, brainstorm, even read a book or play a game. There's never a time when I'm tapping my foot waiting on someone else now (and I'm an impatient person) -- because there's always something I can do on my Treo to keep my business moving along.
Hope this helps,