Ahhh! $9... for a pot?
try digikey.. http://search.digikey.com/scripts/Dk...=potentiometer
select 50k, continuous rotation, click apply filters, then click view page (1).
One of these might work. There are 32 others.
http://search.digikey.com/scripts/Dk...me=987-1322-ND
http://search.digikey.com/scripts/Dk...name=CT2207-ND