Recently, when I was riding my bike, one of the crank arms fell off and I realized that the crank bolt wasn't properly adjusted when I ordered the bike, hence when it fell off, I was able to put the crank arm back in, but the bolt was lost, so I've been searching (bike shops & online) for a new bolt, but I couldn't find it anywhere. The bolt on the other side though displays some sort of details, which displays this:- 28-31ft-lbf 387-428 kgf-cm 38-42 N-m.
I have never seen a crankset with different specs of bolts on either side.
Since you have one, take it out and visit your Local Bike Shop. Ask the mechanic if they have something like that in their scrag bin / junk drawer.
Expect to pay a few dollars but you'll have a bolt that is rated for the purpose. If you get a matching thread bolt from the hardware store it might not be hard enough for the purpose.