Looking for Nest doorbell (battery) terminal screws size

[wyrdfish]

Hi,
My nest doorbell stopped charging and I disconnected it from the power and managed to lose a screw. 

I looked online and it said M3-0.50 x4mm so I ordered some of those and it seems that they are way too big. The real screw is much thinner than M3 more like M2.
Does anyone have the actual size so I can order the right thing?

thanks

Dave

[wyrdfish]

I bought this pack
https://www.amazon.co.uk/dp/B092SGDKY6?psc=1&ref=ppx_yo2ov_dt_b_product_details
I used the M2x4 screws,the head was slightly small, but it held the wires in ok.