It might have class 15 bobbin case. There are stores specalising in screws, bolts and nuts, they have any dimension of threading, widith, lenght, etc. If not they can usually make one.
There are a few intersting early Japanese zigzaggers, but a major part of them develps from a buy up or merging with the White or New Home company (if I remember correctly). I can't remember exactly (needs a bit of investigation). From these there's the Japanese standard evolved and I guess parts will be specific for these models, even if related models often shared parts. Presser feet are often basic low shank, a lot of Singer feet will be compatible.
These old machines are often stuck and sluggish, just take off tops and lids, and give it a few turns of cleaning, oiling and running the machine the next few days and it will run again. If not, inspect parts, you will find the problem area.
You can probably search up a replacement tensioner, it's hard to make your own part. If too many parts are missing it might not be worth the effort, but if it's a nice running model with all metal gears some are willing to invest some time and money to get them up and running again.