This is for anyone wanting to add more handsets to their AT&T CL84100/200/400 DECT6 cordless phone system. Sold by Canadian Tire and Staples among others.
You need part number CL80100 handsets. To order, email your request to firstname.lastname@example.org. As far as I know, no Canadian retailers stock, or will even order CL80100's.
I bought a second CL84200 system (on sale at CTC for $69) just to get the handsets. They won't work with the first base unit. AT&T tech support referred me to Vtech who could not explain why a CL80200 cannot replace an identical CL80200.