887 Plug Size?

[Mark Mags]

So, this is my first year out for deer, and my primary rifle will be a old, handed down break open Cooey 12ga. I will be taking my 887 Remington as a backup, but I need to make a plug for it. Does anyone know the dowel size I need to be looking at? I don't want to be making mulitple trips to Rona...fwiw, I will be using Challenger 2-3/4 rifled slugs.
Thanks gang.

 

[Lead Loader]

3/16 or 1/8" dia works, load 2 shells, put dowel in, mark and cut off