Heres a few sites I found.
Maybe when you get some, you could get a reloading set up and hand load some custon loads for your rifle.

Good Luck.

http://www.midwayusa.com/Find?userSe...y=38+-+40+ammo

I think this is what I would get, --> http://www.sportsmansguide.com/net/cb/cb.aspx?a=244632

http://www.obsoleteammo.com/