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In case anyone's interested, I noticed that there's a transparent version of the F 35-70mm lens listed on eBay:
Pentax SMC AF 35-70mm f3.5-4.5 Transparent Model (item 282838517342)
It has some condition issues (e.g. I see a couple of chips on the zoom ring). Asking price is $770(!), though there is a "Make Offer" link. (I have no connection with the seller.)
Here are some earlier forum threads about these transparent lenses:
Transparent Pentax SFX + SMC F 35-70 (the lens looks nice on the transparent body)
Did Pentax really make a clear lens?