26 mm IS 1", but the European standard is 30 mm. You can get scopes in both 1" and 30 mm tubes, in all price ranges, just measure your existing rings.
As for upgrading a Zeiss scope, what are you going for, Leica?
I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.