KJW MK1 as a sniper sidearm?
 

These things seem pretty decent for their price.
Do they make for reliable/decent sidearms?

Just need something as a backup when playing sniper and don't want to spend a fortune.

No, because they shoot pretty hot. You want a lowered powered (normal powered, like 300fps) sidearm when you're running a high-fps sniper rifle.

Recommendations in the $100 range?

KWA ATP 159$ if ya know where to look, so far i like mine and you dont have to worry about regasing after every mag or so myself and 2 other teamates are getting 4-5 mags outa 1 gas-up and it holds 23 rnds

Berreta PX4. Some websites sell them for a high price but one is selling one one for 167$. You just have to do some research on this kinda stuff.

My recommendation is to save up more money and raise your budget to at least $200 or $250 to get something decent.

any NBB pistol will probably meet your price range. I had a KWC NBB 1911 at one point. You had to gas the gun though, and it had a little stick mag. But it didn't make a lot of noise (something that might help since you're a sniper) and it was cheap and worked well.

There are also a slew of NBB CO2 pistols out there you could probably buy from an outdoors store like cabelas or something.

You won't like the answer..

But any crappy springer at Walmart/Canadian Tire.

They are cheap enough that you won't mind if it breaks.
They are surprizingly reliable, a LOT more than any GBB.
They are quite silent.
Did I mention they are cheap?

They are also quite accurate when inside the MED (say 50m).

Only problem is you have to re-cock the gun after every shot, so unless you can hit your target with the first shot, its prob not the best idea to go springer......if you look around there are the 'old' clear soft GBB pistols available at extremely good prices - like the lineup of KJW pistols with the metal slides and clear lower frames. --? in your price range, dont shoot too hot, semi automatic for when you don't hit your target in the first shot.