While there has been a good measure of jest added to the replies here I did in fact contact David and he sent me what I would call a very good value in the hair.
The fly I use the most is loosely based on the Wilkinson Power Sunray, a tube or hook tied fly. Since I first tried the fly some 7 years ago it has been the best producer of caught trout and steelhead trout as well as occasional Silver Salmon by catch.
I have been tying them in various sizes for years ranging from quite small to some that stream nearly 4" in total length and I've been catching fish. Because I didn't have a bag of Colobus Monkey Hair lying around. The Colobus became in demand during the Victorian era I believe with its long luxurious hair coveted by who else but the fashion industry? The hair has been used by Atlantic Salmon fly tiers for a very long time on patterns like the Dee Monkey named of course for the hair itself. I've tied the Dee Monkey also and for what ever reason the Wilkinson variant seems to outperform the Dee pattern by such a margin I haven't tied a Dee Monkey to my tippet for many years.
Up to this point I've used Cashmere Goat hair which is a reasonable substitute but I can see that this genuine Monkey Hair is superior in texture and the even taper of individual fibers. I took David up on the offer because like many other materials I've used over the past 50 years this animal has been dead for a long time and I can sally forth with no undue feelings of guilt. I haven't tied anything up from it yet in part because my days have been attended by plowing and shoveling the abundant snow supply that is slowly burying us here at home.
I dug up a few images of flies made from the Cashmere Goat and posted below.
I would call those small for this type fly. They take on the look of a leech when in use and the finer the hair the more the fly undulates through the currents.
This would be the same fly albeit a variation from the tubes, tied to a #14 double. It has a bit more of the magenta and blue fox hair and peacock topping with a teal collar different but still effective.
The next image should show the basic look of them when in use. The fly is dry but when they are wet they act like you would expect from hair, they almost pulse with any changes of direction or line manipulation.
And finally, this is one of my 2 fly boxes I depend on for steelhead and trout. A mix of Dee Monkeys and Wilkinson Sunray types. I have another with about 50 of the Wilkinson types in all sizes in it and about 2 dozen on doubles and singles so I can stay legal wherever I fish
Thanks David for a good deal!
Ard