After a cursory search, it looks like you can add Lindsay Graham [0] as a Republican senator questioning election results, as well as Mitch McConnell [1] and Perdue and Loeffler [2].

0 - https://www.usatoday.com/story/news/politics/elections/2020/...

1 - https://www.independent.co.uk/news/world/americas/us-electio...

2 - https://www.nbcnews.com/think/opinion/georgia-s-republican-s...