I've had this CEL pop on for the 2 years I've owned this car. I've replaced the gas cap and the evap purge solenoid (autozone unit) with no change.

The CEL will pop on every hundred miles or so and I'll clear it, although I have gone a few thousand sometimes in the summer. The light never goes out on its own, always has to be cleared.

It pops on more frequently in cold weather than it does in warmer weather it seems.

I don't have a scanner with the ability to command open certain valves so I'm kind of flying blind.

Any common causes that I might try to replace with the parts cannon and see if it works?

 

Without the factory scan tool and/or a smoke machine its very difficult to diagnose an EVAP system. As it sounds like you know, techs generally tend to use the Honda scan tool, connect a smoke machine and operate the various valves/components to isolate each area in the system and find a leak.
It could be the fuel tank pressure sensor, the purge solenoid, the canister vent shut valve, the canister itself. The list goes on.