I can't find one anywhere. I know about livesplit 1, but I need one that I can use in a steam application.

You don’t use timers in a steam application, timers are separate programs that run on your computer. This can either be a web based timer like LiveSplitOne or something else. There aren’t many options for Mac timers anymore unfortunately. Llanfair used to be a decent one, but I don’t think it’s been updated in a long time.

If you’re talking about an Autosplitter, I don’t believe you can use those on a Mac because they require regular LiveSplit. You can run regular LiveSplit through Wine, but I don’t know if the Autosplitter would work in that scenario.