This brings up a couple of things I want to mention ...
First, there is something to be said for using like equipment. In any profession, but especially public safety, equipment can fail at the time you need it the most and having like equipment as your partners/colleagues allows you to rely on them should your equipment to fail. I am pleased to see that you want to use a similar radio as your department. This will make it easier on you if a battery dies, antenna breaks, or you need to borrow an accessory.
Secondly, and I don't want to sound like I am taking a dig at eBay, but do you want to take the risk with an unknown radio? Has the radio been rode hard and put away wet so to speak? Is the radio even flashed correctly for your system and if not, how much will it cost to bring it into compliance with your system? Also, will your department even allow you to use a radio not directly purchased from, a known to them, dealer (they may not want to take the liability of allowing you to use that equipment)?
Finally, and much like my first point, using equipment similar to your department will make programming that much easier for them and you. Using differing radios may not allow you to have a similar talkgroup template or have a similar scan function.
I only mention these items because I went through the same this past fall when I tested/evaluated two alternate radio brands for my department. I can tell you without a doubt the department flat out refused to allow any radio to be bought off eBay and it rested solely with liability reasons. The department did not want to risk officer safety. The ability to swap antennas, speaker mics, belt clips, batteries was also a big factor that I had to look at while evaluating radios. As was the ability to program radios similarly to each other.
If you want we can talk in more detail offline ... just message me.
Matthew