What alternative to 70-200 2.8 ?

I used a Sigma 70-200 2.8 lens for the first time with a Pentax K5 (which is a friend's). Then I could borrow one for my previous camera D7000. I loved shooting with that lens and I loved what I got with it. Soft bokeh and subject separation astonished me.

Now I am using a D700. This time I (albeit briefly) used an old Sigma 70-210mm 2.8 lens, which had no OS or HSM. Nevertheless I enjoyed it still.

Now to the question. I loved using a fast tele and I loved it even more on FF. Normally I always use primes but I see that zoom is more handy in tele lenses. The problem is those lenses are quite heavy and difficult to carry on a street shooting day. Attention-grabbing lens too. But that comes with the territory.

What may I use for an alternative that is not as heavy, big and expensive? Other than the new 70-200 f/4.

Thank you in advance.