Hey all, hoping someone can help me out. 

I'm looking for a way to create the Thundercannon from one of the previous versions of the Artificer class.

One of my players has been playing the same Artificer character for a long time, and while he's agreed to update to the official version of the class, I promised him he could keep his Thundercannon. The only problem is I'm having a hard time designing one with the homebrew creation system. 

Anyone have any tips on this? 

Thank you!