M2.5 x 8mm screws tend to work. Here is a link for 500 screws for AU$119. M2.6 screws are extremely rare, except on expensive hobby websites, and 0.1mm diameter makes hardly any difference. So why not order 500 of them, stainless steel 304 grade with a nice allen key socket? That's around 4 cents per screw. You need not ever pay more than 10 cents per screw, including delivery. So buy a few more for later.

Qty 500 Button Head Socket M2.5 (2.5mm) x 8mm Stainless Steel 304 Screw Bolt

I can't provide links here yet but search for the above phrase or similar on ebay.