I have seen a lot of 35mm equipment on the local craigslist. The Pentax lenses will work on Pentax DSLR's. Another option to check out is KEH as they aggressively advertise buying used equipment. Adorama and B&H also sell used equipment.
KEH's website leads you right to "Wanted: Your used equipment" link.
Good Luck
Looks like Exit and I were typing at the same time. I suspect I type slower
