There are some listed on Tripadvisor. If you google Dublin Pub Crawl Tripadvisor you'll get a list of ones to check out (literary, music, and those just listed as pub crawl). That's my suggestion and I'm sure others may have more concrete companies you can look at! I was looking into one and after reading reviews decided if I want to do a pub crawl I'll create my own... :)

Have fun!