Originally Posted by raymeedc 
No reason to look for any lens other than a Pentax. As mentioned above, Pentax 135-m is commonly available on Ebay in excellent condition for about $50. I picked up one myself a few months ago in mint condition for $46 on Ebay.
There are quite a few reviews of the M 135/3.5 in the lens review database:
Pentax Lens Review Database - 135mm F3.5
Steve
(Surprised no one has suggested the Tair 11A 135/2.8...)