The 66's at Walmart and Joann's might work but if you get them there, keep your receipt as you might just be taking them back. I could wind a bobbin on my 1928 Singer 99 with teh Singer brand 66's at Walmart, but they didn't go around in my bobbin case smoothly. They were too tight a fit to work. I ended up ordering some from Sew Classis, and was very pleased with them as they are of a good quality.
Have fun with your machine. It's cute in the green!
Janis