Water pump pulley, all created equal?

[scoobert]

here is something in my 31 years i have never tried to do before.
i need to move into a 2 groove water pump pulley, so i can run 2 belts on my alternator. i am going from 90 amps, to 200, and 1 V belt will not cut it.
so i need a proper pully to fit my waterpump, any good ideas where i can find one cheap?

here is my alt breakdown.



here is the pulley they sell for the engine with 2 grooves.
Westerbeke, Pulley, Fresh Water Pump 2 Gr, 31110, 031110
very over priced. they also make a 4 belt unit, i would rather have, but it costs $400!!!

[brutb]

You might try this site if you are handy and have all the right dimensions of your pulley
http://www.grainger.com/Grainger/v-belt-pulleys/sheaves

or

Discount Marine Source

Pulley,Fresh Water Pump 2 Gr

Part# JHW-031110
Manufacturer Part# 031110


Regular Price: $300.95
On Sale For: $260.95