I just built two for our team, here is the Radio Shack part numbers/cost:
PC Board Toggle Switch SPST
275-0645 - $3
D-Sub Connector 9 pin male
276-1427 - $2
D-Sub Connector Hood sized to fit
276-1539 - $2
So for each dongle: $7 of parts, a little scrap wire and a little soldering. The first one took 25 minutes, second one took 10 minutes.