[Hallicrafters] HA-20 external coupler info needed

[SChilds938 at aol.com]

I recently picked up a very nice HA-20 VFO/VSWR unit for my SR-400.  
Unfortunately, it did not include the external coupler, so I cannot use the 
SWR/power meter functions.
I have the manual which shows the simple schematic of the coupler unit. 
Unfortunately there is no information on its physical construction.
I'd like to build a coupler...has anyone out there solved this problem 
already?
Ideas appreciated.
Thanks
Steve, W8SEC
SChilds938 at aol.com