Hardware developer RichDevX had released prototype Vita card readers in the past. He confirmed yesterday that hes had a working prototype Micro SD adapter for PS Vita for a while for which a video was published last year, and hinted at plans to manufacture it at scale.

http://wololo.net/2017/05/12/ps-vita...crosd-adapter/

https://twitter.com/RichDevX/status/862208064254095361