I didn't realize that you didn't have some form of central heat in your house, I thought you were looking for an alternative to your Poconno.
I did do some research, HomeDepot.com lists 6" insulated flexible ductwork for $25, and 8" for $29.
I think the outside diameter of the distribution blower housing on your Poconno is about 7-8" . So for $29 and a roll of duct tape you can make a makeshift cold air return.
I guess I'm busted on the $30, I forgot the $4 roll of duct tape.
I would just slide the end of the duct over the outside of the fan housing, duct tape it in place, lift the rest of the flex pipe up to the ceiling of the basement and find a location for a floor vent into the upstairs.
Or just fasten the duct to the ceiling, even drawing the warm air off the ceiling instead of the basement floor will be a huge improvement.
I know I'm lecturing, and I appologize, but it is really so simple to try, and if you are carefull if it doesn't work, you could take it back.
I think you could use cheap dryer vent pipe, insulated pipe is not an absolute necessity. That is what Rouxy did here with great success:
4" dryer vent is really cheap. I'm amazed everytime I read the first post in that thread by Tom Rouxzy.