Where is the purge valve located on a 2004 Buick rendevous

Should be on a crossmember near the gas tank tank.

Follow the fuel vent line (comes from the fuel tank) to the engine,it will be on that line at the engine.

We do not have wiring diagrams here, so I suggest you purchase one to answer this inquiry.

Here is a link for locating/replacing the canister purge solenoid on a 2006 Chevy Impala. I couldn't find a video for your Buick, but I suspect it may be located in the same area - near the fuel filler neck. How To Install Evaporative Emissions Canister Purge Solenoid 2006 12 Chevy...

this is a video of how to find , locate add replacement
http://www.carcarekiosk.com/video/2004_Buick_Rendezvous_CXL_3.6L_V6/fuse_interior/replace

p0443 is a EVAP code. The EVAP system deal with the vapor of your fuel tank. The definition of P0443 is EVAP purge valve circuit malfunction. The purge valve solenoid is locate on a support on the motor. There is 2 plastic hoses, one from the fuel tank and the other going to the trottle body. The most commun cause is a broken wire at the purge valve solenoid connector. The second most commun cause is the purge valve solenoid itself.

EGR is the purge valve.

Engine Compartment ,has a green cap on it

You don't replace anything based on a code

You use trouble charts to diagnose the cause of
the codes & find the problem

hand tighten and then turn 1/4 turn with wrench or until snug

It is in the fuel tank, according to the documentation. It gets replaced with a fuel pump failure.