British Standard Whitworth 5/32 by 32 TPI. Link posted. Note the thread form is rounded at the crest and root. American Standard are sharp even if the same diameter and pitch they will not fit but jam and lock in place usually snapping the bolt.
https://en.wikipedia.org/wiki/Britis...dard_Whitworth
My suggestion is to re-tap and use 8-32 American Standard if you have the room. A slightly larger bolt.
The 5/32 by 32 has a tap drill size of #30 tap drill or .128
The 6-32 uses a #36 tap drill or .106 so you can see the hole is already oversize so that would make the thread sloppy and a poor fit
8-32 requires a #29 tap drill at .136 so you could run the #29 drill down each hole and re-tap it with an 8-32 tap then you could easily find screws just about anywhere. You might even get lucky and just have to run the tap down the holes depending on the material. Be careful not to apply to much force lest you break the tap off in the hole.
My recommendation is to buy the 8-32 tap and #29 tap drill and rework it for the right length 8-32 bolt.
Dennis