You are correct, you need a low-speed 430 RBZ. Assuming you already have the uconnect and bluetooth, it's a very easy swap. Make sure whomever you buy it from gives you the four digit security code or you may have to go to the dealer to unlock it.
They pop up periodically, so just keep an eye out - most go for ~$350 shipped but I believe I did see one sell a month or two ago which would have been in your price range, so it's possible if you catch it fast. They are available on various sites for around the same prices as they go for here, so you can do some searching. Don't forget, there are other vehicles which have the low-speed 430 (the one I bought came out of a Jeep Latitude) so you can do a little searching on the applicable vehicle forums but, as you know, you have to double-check that the vehicle is low-speed BUS.
Good luck - I'm thrilled with the 430 I installed in my ride, I'm sure you will be too once you find one.