Size 15 Narrow width women's slippers in the US
You can get great deals on large size shoes at Amazon with a bit of patience. Their own Amazon Essentials range does fashionable styles at great prices up to size 15 US. The women's shoes department goes right up to 16 US, although many of the largest sizes will either be Chinese brands or unisex. If you have Amazon Prime, many shoes are eligible for free, fast shipping. Plus you can even try before you buy or avail of their personal shopper service.
6pm is the discount division of US giant Zappos. They offer 30-70% off many shoe brands with some styles available up to 16 US, occasionally even larger. Most inventory is made up of closeouts or end of line styles. So quantities are limited & items are not usually restocked. Ships to USA only.