Yup they are very expensive but then since they are constantly recycled in the parts washer it may not be as much of an issue as is generally thought. for a homemade washer I woudl like to use 1/2 of a 55 gal drum so I can put a complete tranny or engine block on the washer. Now one will need to do a secondary cleaning before painting to make sure no solvents are left to interfere with painting. Might be best to just bite the bullet and get a replacement washer pump from your parts supplier as some of the jury rig deals wind up costing as much or more as doing it right in the first place.
I have tried most all of it and now do what is known to work..