Encountered the same problem with some leds having a collar that stops the bulb from being pushed in far enough. Found these on amazon - they fit (among others) Bernina record 600, 730, 801, 900 nova and 1011 - so I reckon pretty well all of the older Bernina that take bayonet fittings. Also fit Husqvarna 19e, 1030, 6570, Optima 150 so fairly sure they'll be OK for other machines in those ranges. Plus Singer latest version of 201,185 and 401g.
Have all those machines so I know they fit.
on Amazon - Bonlux 2W Ba15d LED Bulb 220V-240V - there is a cool white or warm white option. About ~ £8.50 for 2.