Hi Leisacoins! Welcome to the forum.
Interesting to 'meet' a descendant of one of the original bankers. We will be adding Joyce's Bank to the main website before too long, when we have gathered information and background research on it.
Galway notes are quite scarce.
In terms of where to look for the notes, the best places to find them would be either at DNW auctions in London, or Whytes auctions in Dublin. Both auctioneers have sales including Irish notes two or three times a year.
There are other auctioneers also, but these two are the most likely to feature the notes you are looking for. I always add their latest sales which include Irish notes to the
Events Update Thread.