In February 2017 I fitted a SSD to a Z90D7. This is described here.
In February 2021 I heard from Calvin who had come across a Z90S7 that had a factory-fit 60GB SSD. This is described here. Then in March I heard from Piotr who had come across the official Wyse drive mounting kit on a Polish auction site. I've appended the details to the earlier report.
The SSD is positioned where I placed mine - the obvious place bearing in mind the space available. You can see the mounting brackets that hold it in place.
With the SSD removed you can see the cabling. Interestingly Wyse have chosen to use the second SATA data socket and to use CN11 to provide the power for the SSD. I note that they have also chosen to use a longer cable than absolutely necessary with it being folded under the SSD.
In March I heard from Piotr who had come across the official Wyse drive mounting kit on allegro.pl, a Polish auction site. [The original full link now removed as it is no longer valid].
The kit comprises two metal brackets and a SATA cable. Although the two brackets are completely different they are apparently marked 'L' and 'R' (but are you looking from the front or the back? :)
The label on the cable says "Miranda 6017B0325301" but I'm not sure exactly what the official Dell Wyse part number is.
This shows the brackets in place.
The longer bracket fits against the chassis. The mounting point at the rear uses one of the board mounting screws. The one towards the front uses a stand-off pillar. (Looking at the photo of the kit you can see that leg is shorter).
The other bracket only has a single mounting point and is also fixed through a stand-off pillar.
The drive in place.
Piotr also noted:
* standoffs require M2x4 (maybe x5) screw
* brackets are compatible with 9mm 2.5" drives