Hello SusieQ - how frustrating!
Try
http://www.helenhowes-sewingmachines.co.uk. Postage shouldn't be too extortionate. Otherwise I'm sure somebody will come up with a source in the US.
Are you sure the bobbin winder can't be fixed? It sounds as though the two halves are out of alignment or insufficiently secure so that there is no longer enough horizontal pressure to keep the bobbin held tight. If you post photos here people can have a look and make suggestions.