Originally Posted by
ThayerRags
Today they’ll sell you the bulb, but it will only fit into their socket, attached to their machine. It’s that way with most of the new sewing machine parts today.
Pretty sure it's not that: I have a lot of these Singer bayonet bulb machines and any brand of bulb will fit. My local parts supplier only sells two brands. The more expensive is made in Germany, the cheap one is from China. Sounds like she may have found something even cheaper (quality-wise).