The best alternatives to Domain Comet are DomainWatch, Deez, and Moniker. If these 3 options don't work for you, we've listed a few more alternatives below.
DomainWatch makes it easy for you to monitor your own domains and ones you want to acquire. We keep an eye on expiration dates, nameservers, SSL certificates, whois contacts and more. DomainWatch is free for monitoring expiration for 10 domains. If you have more domains and want to monitor more than just expiration dates, say hello.
Moniker is a global leader of domain name services. Moniker makes registering domain names affordable and fast while giving customers the tools needed to win on the Web. Offering domain registrations and tools to access hundreds TLD's, Moniker makes it easy to securely operate and manage your web properties in a single place.