If you intend to replace that rear sight I would like to recommend glow-on.com
I've used them before, plus you'll have enough for lots of gun sights, and it won't cost you a fortune, you can use your original sights.
Here are some pics of my new Kel-Tec PF9 9mm ( is like a mini glock )
Here are the standard ear sight, not fun at all and useles in a dark environment
Like i said I've used the glow-on products before so I did this
Now check it out, day and night difference, hope this helps