How can I lock the FPS of CSGO to lower than 60?

In Counter-Strike: Global Offensive fps_max can limit your FPS, but will only go down to 59. I know this is weird but I can't play on anything more than ~35 fps without getting sick. A lot of friends want me to play with them, but I can't at that high of an FPS

Does anyone have any ideas for how to lock the framerate under 60 FPS?