There is no resource I know of. You may have some luck if you narrow down your search. I was able to find a list (not comprehensive by any means) of Pentax lenses that extend and those that do not. Perhaps if you search internal zoom and different brands, you may have some luck. But every lens is different. Personally, I would pay a hefty premium for any lens that zooms internally. It may sound ludicrous, but I hate the way they look when you see all that smooth plastic when they zoom externally.