You need TPP480
The RIB box you need is called the TPP-480 box. You connect the RIB box to the top of the walkie. There are some direct connect cables available but I've not heard great things about them. Thankfully, Maxon is not as particular about Motorola in needing a door stop computer to program it. I do keep my Pentium M around as it has the best success. You need TPP480 that runs under DOS. You need a dos boot disk or CD. Remember to load the RSS (TPP480) on that disk also or you can just access it on C:. Also remember you need a serial cable to hook the 9 pin connector on the RIB box to your computer. You can try a USB to serial but if you got a serial port on your computer, use it and also use what is called a null modem. It switches the tx/rx lines and makes it work. If you don't do that, it will frustrate you to no end.
I use these TP-4800's for Itac and 8tac purposes, 800 simplex comms, and accessing our local 800 repeaters with no trunking.