You should really think about Scandi fixed blades. There are some that are pretty small yet strong enough for what you need, they aren't any harder to manipulate in small spaces than folders (and you needn't worry about locks failling).
For tough work I would try out one of the Eka folders. I got one they made with Wenger for Wenger's Wood line (it's called "Woods hunter", or something along that line) it's a lock back with a very comfortable handle, which can be easily replaced if you manage to break it. The tip is quite strong and the lock is at the back of the handle, you have to push the lanyard hole to disengage it, so can gorilla-grip it without worrying. You can get a Swede 88 form Ragnar for $29! The Nordic T8 is way more expensive, at 70 bucks, but it rocks!
Buck 110 and 112 are built like tanks, and well within your budget. The tip is a bit fragile, IMHO, but it can be re-ground after you break it. You might want to check out the Buck Mantis and Pilot, they are quite cheap, with 440C blades and SS handles.
How about a Ka-Bar Mule? I don't know how the zytel handle will hold up to the punishment, but the knife is quite sturdy.
The Benchmade Monochrome has SS handles and it seems like a great deal for 33 dollars.
A Vic Soldier would probably be a handy addition to whatever you get. Using its screwdrivers and reamer will probably help to extend your main knive's lifespan.
