Where can I find the size of as well as the location for signage for fire extinguishers ?
Colors, pictograms, wording, letter size, shape and size of sign etc. varies widely if you look at what is available "off the shelf" from sign companies. A perpendicular wall sign should be mounted with the bottom of the sign at least 6' 8" above the floor to meet various code requirements: ADA, LSC, etc.
NFPA 10, Chapter 6. Basic requirement is "conspicuous marking" which leaves the door wide open to differing interpretations by AHJ's or other inspectors as to what is acceptable to their agency. In my experience, a fire extinguisher hanging on a wall in plain sight meets the basic intent. When that same extinguisher is not readily or easily seen because something visually obstructs it then some type of sign, possibly mounted above, may be indicated. Should it be a flat mounted sign or a perpendicular sign? This often depends upon the direction of approach and which sign would be most easily seen by most people.
The same can be said for a fire extinguisher in a cabinet. Some cabinets have markings on their exterior, others do not. Some cabinets have glass doors and the fire extinguisher is readily visible inside, others do not. Some cabinets blend in very well and others clearly stand out.
IMO, working with your AHJ to determine what they find is acceptable is usually more efficient than speculation which more often than not leads to overkill.
Retrieving data ...