As you probably are aware; Aristocraft is no longer in business. There may be some of the "Track bumpers/end of track devices" to be found at dealers, just about any place you can think of.
If you can't find any, just try building a few by yourself. They can be constructed, out of wood, as many of the real ones were. There are pictures to be found all over on Google. Or you can use the picture of the Aristo one, as a guide.
Have fun...it could be a great day's project, sitting at your work bench, or kitchen table. Your partner/wife/girlfriend might object to model building in the bedroom, or dinning room table...beware...!!