Hi,
Thule do a ladder system (548), which I think has a ratchet at one end, & I think a clamp at the other, but you need to have special Thule square or aero roof rack bars.
I have a question though, with those spinning type clamps, are you able to remove the ladder quickly, or do you spend ages spinning up & down the thread? Thet do seem a lot cheaper than Thule.