Siebenrock indeed do an "improved" version at 9.95 euros. However, assuming you have the OEM standard G/S forks, - do check to make sure that the breather tubes for the forks are not blocked (they exit from the top of the the bottom yoke and have small tubes into the headshell) as otherwise the gaiters can prematurely fail due to pneumatic pressure blowing them out, giving the impression that the gaiters are flimsy.
FWIW I give my G/S a right proper hard time off road and the stock BMW gaiters so far are in perfect condition after a few years use.......