There are numerous sea fishing tackle shops across the North West of England and Wales. Most also have a fairly steady supply of fresh and frozen baits. See the interactive map below for locations of bait shops on Anglesey
Some of these are more geared towards baits and rigs whilst others are like Aladdins cave, literally everything within 4 walls. The interactive map below has info on the location and websites of coastal bait and tackle shops on Anglesey. If I have missed you off and you would like adding let me know.