I purchase an M2.5x6 DIN912 SHCS from Metric Screw and Tool Co. ($25 min. order) with a black oxide finish 1-800-METRIC1.

Also, Metric & Multistandard. http://www.metricmcc.com/

Search under Metric Item Only for 912 (the DIN #)

I'd be very suprized to see a bright zinc or uncoated steel socket head cap screw in that size. Stainless and High-Tensile would be more standard.

-Zeke