A substantial amount of information on George Walker's career is provided on the home-pages of the Breiðdalssetur Foundation (Breiðdalssetur ses). The supporting text is mostly in Icelandic and some links are broken, unfortunately.
However, with the aid of AI or similar translators one should be able to figure out what is available there. Among other things there is a list of papers by George Walker with links to pdf's. Also a complete bibliography. There are links to photographic material connected to George's research in Iceland. Furthermore there are links to reports of Walkers trips to Iceland in the fifties and sixties. There you can find a link to a video of Georg Walker giving a lecture on ignimbrites in New Zealand, around 1980.