Hi Phil,
Having done wheel bearings on other vehicles with similar construction I would normally support the collar on a solid surface like the top of an axle stand, then with a sharp cold chisel strike the collar across the narrow bit in 2 places 180d apart. They can then be slid off or move as soon as you start to pull off the bearing. Unfortunately they are not re usable if done this way. I can probably measure a CA one and get some sizes so you could try and source a new one.
Or you could warm up the collar with a torch as the bearing is pulled off. Then use it again with some loctite to guarantee it doesn’t work loose.
Yours
John f