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I have purchased a ton of gear from Roberts / Used Photo Pro. One of my favorite sellers!
If they are low on Pentax brand gear, you might consider doing what I do - experiment with third Party lenses on your Pentax body. Check out their: M42 lenses, Leica R lenses, Zeiss ZF lenses (all are adaptable to Pentax K mounts), AND if you are feeling really experimental you can use inexpensive Bronica SQ lenses on your Pentax body
with an adapter.. The Bronica SQ 150mm f/3.5 "S" is considered to be one of the
best bokeh lenses ever made (I own 3 of them).
Just an option for you...