You could setup the shield around Lagrange point 1 which has the advantage of not creating noticeable rings around the earth. This does not reduce material needed by all that much, but it does prevent kessler syndrome as your sunshade breaks down.

However, a much cheaper option is simply cover large regions of the earth with a reflective coating. Between those extremes are things like hot air balloons in the upper atmosphere.

Or you know, polluting with vast quantities of SOX. You're dreaming too big, and not dirty or dumb enough.