I absolutely hate it when I see a limited edition item or some thing that Disney used to carry that I missed out on when they sold it. This tends to happen to me a lot, so I found some good places to go to to try to find items that I absolutely have to have that aren’t being sold anymore.
My favorite go to is Poshmark. Poshmark specializes in fashion and clothing, has excellent customer service and has everything shipped to you via priority mail. It’s easy to filter down by brand and often times items are very fairly priced and not extremely overpriced like they can be on other sites. It’s not typically the first place people look, so you might be more likely to find that special item because it’s not overcrowded with people searching for Disney items.
I always check eBay to see if I can even find the item. If it’s something that was limited addition, it’s probably going to have a big markup on eBay because there’s probably a ton of people looking for it.
You can often find items on Mercari that are more of individuals listing them that happen to buy the wrong size. I found that it’s often cheaper on Mercari, but goes fast because it’s cheaper and people have filter set to be notified when Disney items go up for sale. You might look out and get it for cheaper here, but chances are the item you’re looking for has already sold.
You can always search Facebook marketplace, but I found that their search engine doesn’t necessarily take you to the right items quickly, so you might have to do a lot of scrolling and editing what you’re searching for to find that special item. That being said, it might not sell as quickly because people can’t find it, which could increase your chances.