Need to extend a SonicWall TZ 400W ( wireless) with Sonic Wave or Sonic Point ?

I manage a small legal office and have a SonicWall TZ 400 wireless that covers the current building ( 15 people on the LANand only one using wifi)
The owner of the company will be expanding into a separate building across a 30 foot Breezeway next door.
I have tested the current TZ 400 Signal and it "peters out" just outside the current office facing the new office space.
 the new office space will only have two people in it)

I cannot move the existing TZ 400 closer to the new building. ( I cannot use the AC wiring to extend the wifi)

QUESTION:  SonicWall just came out with a new "mesh" Sonic "WAVE" that are around $850 each . And it requires yearly fees but support is probably great and an integrated package may make sense.  But I don't even really know if the "Wave" is the right product.  Will a SonicWall Point that not on a ethernet lan act like a mesh ?

But it  seems like a pricey solution  and I might really need two of them ( $1700)
One to boost the TZ 400w inside the edge of the existing office and one to pick up the signal in the new building.
I would like to have a ethernet port from the  device in the new building and would also like to lower the cost (above)
Does anyone suggest the SonicPoint or Ubiquity or Meraki or even Google  Wifi mesh to accomplish this ?