The best alternatives to Flywheel are Namecheap.com, TinyCert, and Tap. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Flywheel?
SeedLegals— Close your next round faster - All your legals in one place
Nodeify allows you to keep track of and monitor any website's SSL certificate. When you register and add a domain into monitoring the app will alert you, based on the notifications you setup, of any updates, issues, and/or upcoming expirations.