I love this Banksia bonsai - am currently trying to grown one myself to bonsai - will be quite a while before it is posted on this blog. I curiously looked what was underplanted - what a beautiful plant. Was told it was Viola Betonicifolia (native violet).
Searched google - as suspected, very hard to find. Only one of the searches led me to a local Indigenous Plant Landscaper, who had this plant in his stock. Unfortunately, they had been damaged by a snail attack, and were looking worse for wear. I didn't mind - will nurture them back to health - so I bought all 5 tubestocks. Hopefully they will survive - as further google searches has come up with no-one else stocking this plant.