Thanks for all the replies. Woody your right they do look similar but there not quite what I'm looking for. Does anyone know where about Rickenbacker used to get there's from?
These knobs may have been made in-house, or at the very least made by someone only for Rickenbacker for I have never seen them on anything other than Rickenbacker products. Some are press-on and some have a set-screw like most knobs you see. If you want a set, they do pop up from time to time on ebay, or if you can find someone parting out a 50's lap steel or console steel maybe you can get them that way.
Someone did make a few super-nice sets of replicas a while back but they have all been spoken for.....
The original runs of knobs will differ from batch to batch, for the ridges/serrations cut into the sides are not all the same.
Thanks for that. I'll keep my eye open on eBay. Is this the same case for the gold trust rod cover too. If anyone has got the original 50's knobs or a gold trust rod cover do let me know if you want to sell them.