Well, there good news, and bad.
First, the good. See that funny circle stamped above the chamber? That is the Imperial Chrysanthemem- symbol of the Emperor. When war ended, rifles that were surrendered had that ground off to prevent shaming the Emperor. Usually having an intact mum indicates weapon captured in combat- and desirable to a collector.
Now the bad news- stocks are scarce. You have some searching ahead of you. Google is your friend. If the rifle is RESTORED to original config, it has some value as a collector's item. As it, it has some value as a shooter or as a parts gun. Would check ebay, craigslist, and post a note on gunauction.com, gunbroker.com, and gunsamerica.com. Also look for an active Arisaka or milsurp forum to check for parts.
Before I did anything, would probably get a smith to check what caliber the rifle is in. Due to shortage of 7.7mm ammo, many were converted to 30-06.
What we have here is... failure- to communicate.