Looking in my spreadsheet, it shows the following:
541678NBL BOBBIN CASE, NO B/LASH SGR. 20U ETC. JAPANESE
541678 BOBBIN CASE, BR, SGR 20U, WHITE, RICCAR ROT
Looking online at the photos for that part number I see bobbin cases that have a "notch" out of them and ones that don't.
google "541678 bobbin case" and click "images"
The bobbin case in my 115 doesn't have that notch. Have you tried it?
It also takes 20U bobbins: 55623S