Hi,
If no markings like the grade 5 & 8 or numbers like 3rd and 4th from left in top left of pic they are standard mild steel bolts. So yes, probably cheap chinese crap. Invest in some grade 5 bolts at least, stainless steel is around grade 5 strength, although for footrests i would use hi tensile steel.
a good set of l/h drills[ wurth,p&n ect ] can work wonders.
I got a set but they are a bit spendy for one off use, amazing how many broken track roller bolts will back out just with the drill.
Question then: Where can I get left hand drill bits (they are not that common)? I do not mind investing in a set.