http://www.buy.com/prod/2-Line-Expan...tml?adid=17653

$25 for a 2-line 5.8Ghz phone.

I ordered one because I've wanted a 3rd expansion phone.
(In my case I have an extra charger from my 1-line Uniden phones of old.)

BTW, it is no longer very expandable,
because they are not making them new any more!