I'd take a look at some oversized seat bags. ortlieb makes a decent one. but depending on what all you are carrying might be no match for a pannier or two.

this thread is a great example of the road bike market turning into an "every road bike needs to be a race bike!!" mindset killing the functionality of bicycles. if everyone wasn't so damned concerned with their bike looking like it belongs in the tdf I think we'd have a lot more happy cyclists who used their bikes for more than occasional recreation rides. (not knocking on the OP at all, just a statement on how marketing has made it harder to get a functional road bike these days)

also, my only bike that is currently ridable is a stiff aluminum road bike with no fender/rack braze ons, and can't fit even remotely wide tires