It's pretty easy to find these lenses with film photos. Go to flickr and search for something like "pentax 31mm ektar".
http://www.flickr.com/search/?q=pent...tar&ss=2&s=int

Or "pentax 31mm portra"
http://www.flickr.com/search/?q=pent...tra&ss=2&s=int

"pentax 77mm portra"
http://www.flickr.com/search/?q=pent...tra&ss=2&s=int

"pentax 43mm 400h"
http://www.flickr.com/search/?q=pent...00h&ss=2&s=int

I'm sure you get the trend now. If you search for a lens and name of film you will find what you want.

From mine, here's I think 77mm...

Cart by Jarek Miszkinis, on Flickr

43mm:

Shave by Jarek Miszkinis, on Flickr

and 31mm:

velvia50_35mm_plus_061.jpg by Jarek Miszkinis, on Flickr