Only needs to be 17 Republicans, as McConnell isn't starting the trial until 1 P.M. on Biden's inauguration day according to a memo floated, so Warnock and Ossoff will likely be seated by the time voting actually starts (which, the Senate majority shifting power in the middle of a trial is weird in it's own right).
The only people I can think of are Romney, Murkowski, Toomey, Sasse, Collins, Grassley, and Burr. My guess is that the rest will take Lindsey Graham's "move forward and unite the country" platform or Hawley/Tuberville/Cruz/etc.'s "Trump did nothing wrong these were proud American's" platform.