I don't find a pump to be much good in cold weather either actually. I mean, if you just pump it and shoot, no problem. But if you pump it and then (because you are walking in the woods for example) don't shoot it for say 20 minutes, its has very little oomph left once that air cools down.
That would be because your seals are leaking, not because the air cooled down.
Fix the seals and you'll have better results.
To the OP. What kind of target practice? Just trigger time? Match pistol target shooting? Just for fun?
Take a look at the IZH 46 or 46M target guns. They are very accurate, only require a single stroke to charge, and have decent velocity for what they do (under 500 fps).
They offer a pretty good midpoint between the 'toy' airguns and the full-bore "Match Grade" guns. Easy to use, cheap to feed. No scuba tanks or air pumps to deal with.
On the far cheaper side of things, look at a used, older Crosman 1322, for a pump up pneumatic, or a new 2240 if you don't mind dealing with CO2 carts.
22 caliber. Since you are limited to 499 fps, the only way you can increase the downrange energy, is to chuck a heavier pellet. This is bearing on the idea that you want to use the pistol for pest control of any sort.
The 2240 platform has got to be the most used modding platform out there. Got a bit in common with the 10/22 in that respect. You can easily spend a bunch more on accessories, than on the pistol itself.
Cheers
Trev