We purchased spares on ebay at one time a few years ago...probably too long ago now but might be worth a look. For example, our tent is coming to the end of it's life but not ready to replace yet. When we do, we may opt to sell poles for spares. Doesn't help you but gives example of why some may sell.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.