Optima House alarm key lost?

System = over 17 years old.
Panic alarm (2 fingers) key lost.
Do you know where i can get replacement key?
Standard across all optima's 2-finger panic alarms? Or different for each installation?

Main problem is house alarm recently alarmed (ext. bell) immediately on entry (instead of usual approx. 30sec delay) + then random alarm (ext bell) while *not* activated, inc. apparently when 1 light switched on. So I tested panic alarm by pushing in 2 fingers, which has at least stopped alarm going off, but also left in unusable mode = "activated" light on but not setoff + no keypad response.
Thanks for any ideas / info.