Try SmartGit. I don't know how it compares with Tower, but it is very powerful and easy to use. I like the way it integrates Git features into a consistent view. For example, stashes and reflog commits can be viewed and manipulated in the same log view as any other commits.

They offer both purchase and subscription models, and a free license for open source work. Runs on Mac, Windows and Linux. I've been using it for years and have always been very pleased.