You can get old impulses, usually with a hoard of aftermarket stuff, for like 60-80 bux.
If they didn't shoot so well, I wouldn't own any as they are Gardner spawn.
Reliable too. I've seen kids and "adults" screw in co2 (not anti siphon) with the gun pointed down, drowning the guts with liquid co2, during winter. They shot fine. Week after week.