1982 Merc 7.5, .438" driveshaft, water pump job

[msease]

I am looking for a water pump housing and impeller for this .438 shaft setup and am not finding it readily available. A brilliant one has ran sand thru this to the point of catastrophic meltdown.
Are there parts out there for this job? How canI get my hands on a new pump housing and impeller?

 

[faztbullet]

18-3054 is the aftermarket impeller but housing(46-92970a1) will have to come from a Merc dealer...

 

[faztbullet]

Thats for the larger id impeller....Merc does not show a repair kit for the small id impeller on separate pieces.