First aid on site
Have you considered this? You can easily buy fully stocked first aid kits for the number of personnel you have on site, accompanied by the accident book of course, this will be determined by number of personnel and distance between office and site.
Quite often I see some effort to archive this however it is normally ill stocked due to use and not being checked, which also raises the question if it’s being used and there is no information in the accident book, your workforce are not reporting correctly.
I suggest you have a formal procedure for initiating site first aiders suitable equipment and emergency procedures these then need to be communicated to all on site preferably during induction