Now that I have your attention, I have located a place to buy the elusive 1.5" stainless steel threaded cross, which can be used as a 1 intake to 3 output manifold, perfect for a 3 impeller pump system (should actually have the flow for a 4 pump system, but you would have to then add a 1.5" T as well). These are great, because they take up a lot less space than the common alternative, the 2 T system. You would likely add 3 1.5" to 1" reducing bushings and then attach 1" hose barbs to the bushings (this is my plan). This is very close substitute for Wake_fun's famous manifold for those of us who have no welding skills or equipment, although it will take up a bit more space than his.
At any rate, I found this item at a very good price, but the catch is I have to order a minimum of 10 to get that price. 1 of these on Amazon.com (best price I have seen on a single) is $48.73, eligible for free shipping with Amazon Prime. For those of you in the Continental U.S., if I can get 9 others willing to commit, I should be able to get one of these shipped to you for $25. Please let me know if you want one.