here is what i would do. take your horseman body to a hardware store and look for screws like the ones in the attached image. you will need to sample different pitch threads but once you have the correct size(metric vs non metric) and correct pitch thread(fine vs coarse thread) buy 4 in the length needed. a bit time . consuming buy fairly easy. You can simplify the process by contacting horseman and ask them which screw thread the body has then simply buy the correct length at a hardware store.
I would definitely suggest inquiring with the dealer you work with (or Horseman, if you have no dealer) to get the OEM screws or at least the specs for locally sourced replacements.
Randomly trying different screws is a good way to partially or fully strip the holes or otherwise get yourself into a frustrating situation. I'll grant you it's not exactly rocket science, but trust me when I say that I've seen easier things lead to bad situations over the last 13 years.
