I need a radar detector

For some odd reason, the speedometer on my car has gone out. We have tried everything to fix it but to no avail, it will not work. You have no idea how stressed I get when I am driving down the road and a police car is behind me. My palms get sweaty and I have this sinking feeling in the pit of my stomach. I stress so much about getting a ticket to the point I drive under the speed limit the majority of the time since sometimes my speedometer will start working and I will notice I usually drive five miles under the speed limit. My husband has decided to start searching for the best radar detector since that is going to be one of his gifts to me for Christmas. We have said for a while now I needed one but we just have not had the money to purchase one, but this Christmas come hell or high water it will be wrapped under the tree for me!