Right, Kenwood, Icom, even the Chinese radios might be a more realistic choice at this point.
I've picked up used Motorola CDM-750 VHF radios for $100. They only do 4 channels. Sometimes you can find them for that price with the accessories, but you are still going to need someone to do the programming for you. If you are really lucky, you can find someone to do it for free locally. I've done a few for other amateurs, GMRS, etc for free, or for the cost of shipping it back.
I agree, though, $100 bucks for a radio including the accessories, programming, etc. is a bit low. Step that expectation up to $150 or $200 and you'll have better luck.
Don't rule out the other brands, though. Motorola's are nice radios, but you will pay a premium. There are perfectly suitable radios from the other brands that will do exactly what you need at a lower price. Nothing at all wrong with Kenwood, Icom, etc.
You -DO- need to have a narrow band capable radio, this isn't an option. Since you will be working under your departments license (you have their permission, right?) you need to follow all the rules or you can get your department in trouble. Narrow band is required. Trying to use a wide band only radio on narrow band systems is going to sound pretty bad. You don't want to be know as "the guy with the crappy sounding radio".
There are some narrow band MaxTrac's out there, but they are pretty rare. You won't find them as cheap as the wide band only models. There are better choices anyway.
Check around with local radio shops and see if they can help you out. Sometimes they have old radios pulled out of systems they've upgraded they'll sell for cheap.
Don't forget to figure in the cost of installation supplies. You still need a suitable antenna for it to work, power cabling, etc.