If you are looking for a single figures well-reviewed headphone case, this Ginsco headphone carrying case is going for $8 by Amazon actual and Prime eligible and not an add-on item. Non-Prime members have the usual $25+ free shipping limitation. Better yet, they are eligible for “Subscribe and Save”, so if you are fond of that way of shopping, you can get a discount depending on how many “Sub-n-Saves” you have going on.

It averages 4.1 out of 5 based on nearly 400 customer reviews and it has 45 answered questions. Check dimensions and reviews and answers to see what it fits and what it doesn’t. The product description gives as examples the Sony XB950B1/N1, Grado SR80, Bose QC25 and Cowin E7.

Based on the product pictures, it works with some headphones that won’t fold flat as well:

PS: I added it to my shopping list for my next Amazon purchase with review coming after I receive it.