I have those typical rear trailer oblong type lights that were supplied from my manufacturer. Stupidly I have lost two of the long bolts that hold the covering lamps on. They are not m4 or m5 and my thread identifier tool doesn't match it. they have flat screwdriver heads on them.

Any ideas?

Possible a BA thread - possibly a 2BA - often used for electrical connectors, PC cases and Electrical enclosures.

http://en.wikipedia.org/wiki/British_Association_screw_threads

[Edited on 18/3/15 by Ugg10]

More likely 4BA.