I wrote to LensRentals about the possibility of having a Pentax mount Sigma 150-500 and a DA 560 f/5.6 available for rent. This is what Tyler responded:
Tyler Beckman, Nov 04 08:43 pm (CST):
Hey Steve, after reading your email, I placed an order for a Sigma 150-500mm lens for Pentax cameras. We should have it listed on our site and available for renting within a few business days. Thanks for the recommendation!
I can't commit to stocking the new 560mm lens just yet, but there's a chance we'll have it stocked sometime next year.
Tyler Beckman
LensRentals.com
How about that?