I have one of those plastic ones as well - probably as old as yours! I would look on CL or freecycle. Seems I've seen them listed on either/both sites relatively frequently.
Or, as others have suggested, check out the big box home stores. You also might want to check Tractor Supply. They seem to be a nice cross of the old fashioned hardware store and the big box stores. Might have something more sewing-friendly??