IMO, rifle size red dots like Eotechs are way to big and heavy for pistols. Check this guy's site, he sells a little red dot called the RDP-II that has gotten good reviews and it's priced right at $139. It's very small and it comes with a mount for a picatinny rail.
It's the 3rd one down the page. Tactical Night Vision Red Dot Sites Page
If you want to spend a little more money check the JPoint, it's even smaller and weighs hardly anything. I had one for a while and they're top notch. http://www.jprifles.com/1.6.1.php