Where and what type of portable air conditioner should I buy?

For $200 you CAN'T buy a portable A/C big enough for a ONE CAR insulated garage.

In any case, a means to pump the heat out of the room is THE ABSOLUTE requirement for any type of A/C.

Most portable units use a hose that can be routed out a window or through the wall.

Just search portable A/C. You can pick them up at most big box stores. As far as brand I wouldn't be to concerned about that like most things the covers might look different from brand to brand. But most probably came from same factory just popped different covers on them.

You'll need access to a window or a vent hole cut to vent the condenser air if you want the unit to operate efficiently. Since the exhaust has the heat an the humidity removed from the room.

Google the home improvement store with four letters that starts with an L. They have a HUGE selection of AC's.

Like Spock said, if you don't have a window or vent you can put the portable's exhaust duct through, you're done. The AC unit HAS to be able to put that hot air outside.

For the record, I don't recommend portable units at all, as they aren't as effective as even a cheap window unit. If you can get past your determination to not have a window unit, you can get a better result by turning to that solution.

all air conditioners work by moving heat from inside to outside. that means they MUST have some connection between inside and outside -- if only refrigerant piping. so if you can't put one in a window ... where can you run the required connection between inside and outside?

btw, where are you? climate probably makes a big difference in your choices