Beemermark
Veteran
I also recommend the 90mm 4.0 Elmar if you can find a clean, post-war specimen. They are very small, light, and are rather sharp, albeit not real contrasty. I don't see too many Canon and Nikon LTM lenses under 135mm for sale in the price range you are seeking.
I wish when someone starts a thread asking for a "cheap" lens would define cheap, it's a very relative term.
Thats said the 90 elmar is a great, small lens that goes for not much. An even better lens, even smaller that goes for around $200 is the Minolta CLE 90/4. I have one (and the latest style 90 /2.8 Leica) and usually carry the Minolta lens. Just as good and a heck of a lot smaller.