I'd look into the Hultafors Craftsman VMK-GH. It's meant for work on construction sites etc. Under ten bucks (at least here in Europe it is about 7 euros). Fixed blade from SK5 carbon steel, sharp as hell, very comfortable handle from hard orange plastic with a nice rubber finish, good forward finger guard to prevent slippage, spine works well as a scraper. As cheap as they are you can get half a dozen and not worry about breaking or losing it. These are a bit like Moras but with a somewhat higher grind, thus keener, with a secondary microbevel that makes them hold their edge longer, and the SK5 tool steel is very tough. The blade is narrower than a Mora Companion, so you can get into confines spaces easier. Very good for very fine shaving cuts, and for cutting hoses and so on. Comes with a plastic sheath. Won't scratch paint as it has no clip and no hard edges on the sheath either. If you have an overall with buttons the sheath will clip to one. Given how light it is you could also just carry it as a neck knife on a length of paracord, under your overalls.
Look at
http://www.hultafors.com/hand-tools/knives-blades/craftsmans-knife-hvk-gh/. They may be a bit difficult to find in the US. Otherwise the Hultafors OK4 'Expedition Knife' (or just Outdoor Knife) is a bit easier to find with camping gear sellers. About 25 dollars, thicker blade (3 mm instead of 2), longer tang, similar comfortable handle, sheath with a nylon belt loop and firesteel loop. For detailed cuts and careless dirty work I prefer the Craftsman. Hultafors has a choice of professional knives on their site, interesting to look at. Not ooh-raah bushcraft/survival stuff, just tools. Which seems to be what you are looking for.
For sharpening 'in the field' I use a narrow hardfoam nail file/pad in 100/180 grit. These won't tear up your pockets or damage anything else, the way a metal file would. Quick and dirty, you can polish the edge when you get back to base and your stones and strop but to maintain a working edge on a blade during hard use, it works well.
Good luck with your new job.