I have a Taurus PT140 that I bought Used. I checked it out pretty thoroughly and it looked fine. As I pulled it out today to shoot, I noticed that the rear sight was not centered on the slide. Then I noticed it was loose. I tried to take an allen wrench to tighten it a bit, but it wouldn't budge. When I tried to back it out to remove the sight the allen wrench started clicking as I turned. It's not grabbing the edges of the hex nut. It's stripped out! 1. How do I go about getting it to come out? 2. Does anyone know where I can get relatively inexpensive replacement sights? Budgets a little tight right now. Thanks guys!