Why don't you have a look at ebay and look for the 150SF ?
I got mine cheap.....
The 150SF and the Imagon are related, I will test both early september in Holland: I have the 150SF and got a 200mm for my Rollei SL66.
(and a 250mm for 4x5")
Basicly the Imagon is a kitted anachromat, a + lens kitted to a - lens, and both lenses are of diferent types of glas.