[Arran]

Regarding the knobs, the two concentric black knobs are Philco, the three brown ones are generic Bakelite knobs, though I think some Airline models used them as stock but with the functions engraved into them. In terms of finding replacements I would post an ad on here, or play the fleabay crap shoot, or wait until the Antique Radio club of Illinois has one of their swap meets and see if you can pick up some there. I think $10 each is too much for repros, it's even a little high for originals, since they are among the most common style of Philco knob out there. Another possibility would be to pick up a junk set or chassis, which might solve the dial glass problem too if it happens to be a 610B or 610T (I don't know about a 610L or 610X), but lots of Philcos built between 1936 and 1940 used the same style of knob.
Regards
Arran