I seem to remember Martin (Martamp) posting ages ago that those Diago PS units can be bought from Rapid Electronics at much lower cost (apparently Diago just re-brand the PS ???)
Yes, , they were £8.50 last time I bought a couple, but the one I used to get (85-2942) has been discontinued.
They do other 9V SMPS's, but I've had trouble with clock noise on at least one that they do.
Johnny Shredfreak doesn't seem to do them any more either.