I have a bobbin winder- only use it sometimes.
I usually by by bobbins prewound. 8 or 10 bobbins for around $5.50. They seem to last a long time. Guess I do not quilt enough because a package last me about a year.
They are the Class 15 style - 100% cotton.
I know I can order online cheaper- but then you have to get so many of them.