A few weeks ago, I was reading Leisenring's book (again) and he mentioned that he got his hooks from London.
The manufacturer he mentioned was taken over by Veniard. So I had a look at the Veniard site on the web.
Veniard is purely a wholesale supplier to the trade, but the site is still interesting reading.
By pure coincidence, they were announcing their hooks being available after many years of closure.
As Leisenring himself had recommended their hooks, I immediately searched for them.
They are a range of old fashioned patterns, superb hooks at very reasonable prices.
I had mentioned this to Jim Slattery and he said that he was a Veniard dealer.
He was going to find out if and when they would be available in the USA.
By the way, Leisenring said in his book, that he preferred down eyed hooks.
He never dressed a Flymph in his life.
Here is Veniards - http://www.veniard.com/section181/osprey-hooks