You could put one in a plastic bag and seal it.  It did get a bit warm but worked fine. Did it for a few days.  You'd also need an outdoor electrical box with a deep "in use" cover that would seal over the wire and protect the plug.

Also, why wouldn't it work through bricks?  I get good signal through 2 layers of solid aluminun foil  insulation, sheetrock and outdoor wall board also with a layer of aluminum foil. I'd think 3 layers of foil would be just as bad or worse than solid brick.
 

We do have outdoor AP units such as the EAP110 Outdoor or the EAP225 Outdoor, which are SMB products. Unfortuantely, we do not have a unit designed to work with Deco in a outdoor setting.

@Tony Hi Tony, I am not clear on your point are you saying that the EAP225 AP outdoor will work with the Deco M9 Units or it will Not work with any deco units?   I have 3 deco units in my home even near the wall, but to reach the pool area, it is at least 125ft away so i would like to put a unit outside the back of the house at least during the summer months.  Is that feasible and will the EAP225 be a good choice?

@RTZ 

The point of the EAP225-Outdoor is it working in terms of the wireless mesh network. So you would just run an Ethernet cable from one of your Deco nodes out to where the EAP will be installed, and that should work. When you go outside your device may not switch over to the outdoor automatically if you name the EAP the same as the Deco. I would name the EAP something completely different or you might have issues of people being outside, but their device is still holding onto the Deco network or vice versa.

@Tony put in a request for TP Link to be the first with an outdoor mesh unit. I'd buy 2 of them. My wifi doesn't like going through my plaster walls and my cement siding.

@Tony There is a serious need for outdoor WiFi 6 units that work with DECO. Cheers.

@Tony 
The status of no outdoor access point for the DECO M5 range was a year ago. Iss there now a product which offers an outdoor accesspoint which I can connect to my Deco network?

  @Tony how's that coming?

Deco X50 Outdoor should be out soon (I Hope!)
https://www.tp-link.com/us/deco-mesh-wifi/product-family/deco-x50-outdoor/