I think the MacBook Air uses a PCIe SSD and I'm not really sure there are any external options for this.
I'm not sure about the SSD apple uses but most of the PCIe SSDs seem to use the new M.2 standard. I'm only aware of the newest X99 motherboards actually offering M.2 support.
I'm just going off of a few brief articles I read on the subject though. Hopefully somebody else can chime in with a more concrete answer.
Seems like OWC will soon release a replacement card. They usually have a matching external case. You might want to give them a call. There customer service is usually very helpful.
While I understand your frustration - your OWC comment is besides the point.
The OP is looking for an enclosure and not a replacement SSD.
BTW I have used OWC on purchases totaling a couple of thousand $ and have never had any issue at all.
They are also very responsive and get generally good feedback on this board.