Well, depending on your budget, the cheapest I can think of are the old SLR lenses, but the tradeoff is that they are often big, because of the adapter. A quick check on the internet will get you the following:
Canon FD 35mm F2
Olympus OM 35mm F2
Minolta MD 35mm F1.8
Pentax Takumar 35mm F2
For a smaller package on the NEX, and a more vintage look, you can go for the 1960s-era
Olympus Pen F 38mm F1.8, or 40mm F1.4. They are generally around $300. If you really like Pen Fs, their fastest is the 42mm F1.2, but typically go for more than $600 on eBay. But just bear in mind that their rendering is very classic, and being old lenses, they often have little or not coating, so contrast may be affected.
I think you can check out old Soviet LTMs too, but their quality vary greatly, and the minimum focus distance is more than 0.7m, unlike the lenses above.
You can go Ebay to check how much people are selling the above.
oh, before I forget, the cheapest 35mm lenses you will be able to find are the
Fujian 35mm F1.7 CCTV lenses. They are like around
$50 to $60 on eBay. but no cool factor la, and lense quality not guaranteed. Good lense for those who want to try out manual lenses.
