WV Dual Flush Pushrod Mechanism?

The 'small flush' on the dual flush has stopped working and the 'big flush' is getting weaker. I want to replace it. WC is a yr old Ideal Standard loo with a 1.5" hole for the push buttom on the top of the loo. I cannot find a replacement mechanism with pushrods on the market. Can anyone help please? Would it be possible to replace the old mechanism with one that has a 'tube' attaching the buttons to the mechanism instead of pushrods? Any help appreciated. Thanks. Roger