Did you find out which size was required?
You have broken our Necro rule so I moved your question to a new thread. Here is what I could find.
From the link:
The correct screw size is 2.0 x 3mm (CM2x3-3.3).
However:
The 8910 service manual has a diagram on replacing the SSD and it shows that you need a M2 x 2.5 screw. You also need the standoff that connects to the hole on the motherboard and allows the SSD card to sit horizontal to the motherboard when the M2 x 2.5 screw is tightened.
So from these articles it seems that the length of the screw is what fluxuates depending on the motherboard.
Your best bet might be to do the same thing as what the OP did and order a multi pack.