Hi Phil,
From the poor photos in ads that I have seen the knobs were probably bakelite. I have outer knobs that look similar and for the time being I may turn some inner knobs from plastic and paint them black. Since finding pictures and information on the Ferguson radios is difficult I would expect finding original knobs near impossible.
The Ferguson Ten I am working on has an interesting chassis also. In three sections, a mix of wood and bakelite with lots of copper shielding. I don’t think Ferguson made low budget radios.
Ed.