Missing intake manifold bolt query

HELP.
I have a very old push mower that I am servicing for a neighbour and have noticed there is a missing bolt that holds the intake manifold in place.
The only model number I can see is VAN 35 E-36102B
I wonder if anyone can identify it so that I can source one?
I've tried to upload a photo but for some reason it won't let me.
Cheers,
TC

Is it one of the two bolts holding the manifold to the block, OR carb to manifold?
 
In any event, they wouldn't be metric and you already have one there to match up with.
 
The manifold to block bolt is usually 1/4 x 20 thread pitch, manifold to carb is also 1/4" but often fine thread..
 
I'd just match one up at the hardware store..
 
.