You just have to fool around on the internet and find one that looks like it. Many--almost all-that look the same are the same. Brillion is unique in that what was made is generally still made and parts are still available because they were used in so many of the same models. Relax.
You have needle bearings that, from a lack of grease, stopped rolling. Then the axles just rode over the bearings that were not turning and wore them out. The rebuild kits come with enough to do the job and you can only fit so many in the hub. Put in what fits tight and that's the right number. You'll see.
Wait--you might be talking about the packer wheels that contact the ground and yes, you could be missing some. Many that look like that are the same and new ones are maybe $85 but used ones can be had for $50-$60. Shipping is an issue because they are heavy. They install by unbolting the axle and sliding them on. No big deal.
Could be but on their basic models a shocking number of parts are interchangeable by virtue of few changes in the models. If I am not mistaken, one needle bearing numbers covers all packers that used them. I've taken a lot of these apart and only recall one number. Sure, new and different models are made but lots still use the same parts. For example, the Brillion "pulvimulcher" of the 1960's is almost exactly the same today, except they are now roller bearings. They make wonderful products and are a fine company.