Here are a couple links. Keep in mind that original Lucas are metric and some of the reproductions are not. The two are a bit different but should compliment one another if you have both types in your dash.
I believe these are the correct Lucas slotted rings. Switches fitting 14.5mm holes. Currently out of stock but I purchased most of my switches from these guys and they should be able to help you. Send them an email. They are pretty good about getting back to you.
http://www.autoelectricalspares.co.u...hes-2565-p.asp
These should fit the Standard thread pitch toggles that fit the 1/2" hole
https://www.tubesandmore.com/product...-switch-chrome
Correction: These will not fit Original Toggle Switches but look correct.
https://www.holden.co.uk/displayprod...?pCode=020.258
I suppose you could also just buy a couple extra simple Lucas toggle switches. Would end up paying $12 per ring. Remember to reach out and verify metric or standard.
https://www.ebay.com/itm/MG-Toggle-S...wAAOSwGotWlogE
https://www.ebay.com/itm/lucas-SPB20...MAAOxy4fBTktuU