Can't locate replacement shower diverter
Recently had a running tub in guest shower of my older home (`60's). I purchased a 3 handle rebuild kit that came with 3 valves, new seats, trim plates, sleeve covers and new knobs. Everything went in great except the diverter valve from the kit doesn't thread in and nothing at 2 local stores looks compatible (tried ace hardware & home depot). Additionally the old valve leaks a bit as water comes out of the tub spout when using the shower, and when I was taking it apart the knob was seized onto the splined end so I had to break the splined end off to remove the knob, so now I'm really stuck!
I found a link on here to a shop in NY arpny.com that has an online catalog of valves. I believe I have ID'd the valve as an Arrowhead Brass ARR5003 but I can't seem to find anywhere online to purchase this, and the arrowhead brass website I found doesn't even list diverter valves.
Can anyone help? :)
Here's a picture of the old valve vs the one from the catalog for comparison - note the splined end I had to break off to remove the old knob.