I understand about sentimentality...
as for the ammo, get ready... Norma is about the only factory ammo and it runs about $2 each. $40 a box of 20. I have not noticed if any custom handloaders load this, but I think the ammo will run about $2 each when you can find it. by the way, what spring was broken?
Scott over at Wanamaker guns might possibly have the correct spring for it. He has collected Japanese rifles for a long time.