Here is a link to the Soundstream website showing all the authorized dealers in the USA. Enter your location in the Your location search box and then click on Search to get a list of authorized dealers within a 50 mile radius of your location (or whatever distance between 10 -500 mile that you prefer).
I suggest that you start contacting them regarding your problem and see if they can be of some assistance to you. There is very little information online regarding parts for your device, so this may be your best bet. It may be that you are lucky and that one of them may know where to get the part from or may have the part from the same model that they use to salvage from for spares. It never hurts to ask.
Hopefully this is of some help.