I got my Sidewinder from Hancock's for $19.95--it's pretty lightweight and junky but it does the job. There's a new model that I haven't seen but is supposedly better. You just have to watch the Sidewinder to be sure the thread is winding on the bobbin evenly. You might have to help guide the thread with your hand--but it's cheaper than taking your machine in for repairs. Hope you've gotten the problem solved.
Dana