Stay away from the Singer branded metal bobbins sold in stores. They're narrow too and the quality control is poor.
People here recommend Sewclassic.com for good quality bobbins. I filed down the bobbin winder on my Singer 66 because I was having the same problem with narrow bobbins. I thought the problem was with the machine
. You would think the bobbins sold by Singer would fit properly right? After I did that I saw some other class 66 bobbins at my LQS and they appeared to be wider than what I was used to seeing. I'll try those the next time I buy that size bobbin.
Rodney