All bobbin cases are not the same. And use of the wrongly fitting case will have unfortunate results. The slightest difference can wreck havoc. That said, the following page offers a bobbin case that purportedly fits several brands including Montgomery Ward. https://www.vintagesingerparts.com/collections/montgomery-wards-sewing-machine-parts
Other than that, I suggest you take the part you are attempting to replace to a service shop and see if they have a match. Indeed, if you make a purchase at the link above, I would recommned you carefully compare the two bobbins once in hand. Alternatives include buying a parts machine. Although Montgomery Ward was bought in 2004, it is unlikely vintage stock is available through the buying entity. Ebay has several of these machines for your consideration.
Answers & Comments
All bobbin cases are not the same. And use of the wrongly fitting case will have unfortunate results. The slightest difference can wreck havoc. That said, the following page offers a bobbin case that purportedly fits several brands including Montgomery Ward.
https://www.vintagesingerparts.com/collections/montgomery-wards-sewing-machine-parts
Other than that, I suggest you take the part you are attempting to replace to a service shop and see if they have a match. Indeed, if you make a purchase at the link above, I would recommned you carefully compare the two bobbins once in hand. Alternatives include buying a parts machine. Although Montgomery Ward was bought in 2004, it is unlikely vintage stock is available through the buying entity. Ebay has several of these machines for your consideration.