A square wave has all odd harmonics 3rd, 5th, 7th e.t.c.
If you construct your sine wave from 4 steps rather just high and low like 0, +1, 0,-1 , you only have to filter the 5th, 7th e.t.c.
You may want to use an elliptical or Cauer filter, which has deep notches in the stop band
You can use almost any opamp (providing its fast enough). The difficulty is the precision resistors and capacitors.