Looking to build a better power supply from an old one

[NZ0T]

I have an old off brand linear power supply that is inop - it was a freebie.  I would like to re-build it with a modern circuit as it was regulated with a zener and I would prefer an ic based regulator.  The transformer is fine.  I would like to find a circuit board I can populate with - parts.  I can build a kit just fine but I'm lousy at breadboarding a circuit from a schematic.  Does anyone know of a place I could find something like that for a 20 amp regulated linear supply?

73 Bill NZ0T