Is there a way to get the other airline PNR myself from co.com?

I book a flight CLE-EWR-ATH-CAI, on CO to ATH then Aegean onward to CAI. I need the Aegean PNR to see seat maps.

Normally I phone CO and they give it to me, but in another thread here about United/CO upgrades, someone mentioned logging in into CO to get the united PNR....and I've never seen how to find that myself.