Re: sig hammerli trailside
It is hard to beat the Leupold pistol scopes. They are rugged, reliable, will hold zero even on heavy-recoiling handguns, and the price isn't too bad for what you get. Whether you go with the Leupold fixed 2x, fixed 4x or a variable is your call.
I also like the Burris pistol scopes which are in approximately the same price range as the Leupy. Burris offers fixed 2x, 4x and several different variables, including a 1.5-4x that is pretty nice and gives you a little more flexibility with your optic on your pistol.
Just take a careful look at your pistol's size in comparison with any optic you are considering. The Leupolds run around 8.5" or so in length for the fixed power (same for the Burris scopes), but if you get into variables, you can get into an 11"+ long scope quickly which will: 1) feel like crap on a .22lr pistol; 2) could effect your accuracy with the pistol because of the feel; and 3) look odd too.
You should also consider the holographic sights which can be great for hunting as long as you don't need the magnification (and obviously depending on the max range you plan on using your Trailside). The holographic also gives you a sight that you can compete with on your pistol. I like the UltraDot Pan-A-V 4-reticle sight if you are considering going that route.