The PS-9000 uses an obsolete regulator made by Fairchild electronics, the UA78GKC, see picture above.  There are work arounds but if you do not mount the 4 terminal regulator on the heat sink then you lose the over-temp sensing.    Typically this regulator will cost anywhere from 40 to 65 dollars. Heathkit had a bad habit of using odd ball power connectors on this series which I have not been able to find, see picture above.  The fluorescent displays are Futaba and are obsolete, even if Futaba still sold them they only sell to OEMs.

One final thought.  If you plan on buying one of these supplies try to find a non-smoker who owned it. I thought the displays were dim and dying but it turned out to be a thick layer of smoke on the inside glass.

If you need a regulator I have a few of them, they are $20 each including shipping to CONUS.

This is another rig I regret selling!