Are you asking about the collar that goes between the inner and outer bearings on the hub? If so... are you aware that they are ground to a precise length to work with a specific set of bearings? That's the reason you aren't finding a separate part... they're sold matched to a paired bearing assembly/kit.
I'm afraid your best and safest choice is to buy a new front bearing for your car. When you order the bearing you'll get "two bearings and the spacer" or "two bearings with extended inner races" depending on the supplier and bearing type.
If you're trying to salvage a set of bearings and don't want to buy a new kit, the only option you have is to take a complete bearing set, CAREFULLY measure the width of the assembled pair (with spacer) then calculate the exact length you need to replace the spacer your bearings are missing.
I wish I could help but I don't even have any used bearings I can even measure for you.