Internal cistern water inlet

Have just taken delivery of expensive new GSI Traccia close coupled wc.
It has no holes for water inlet (tap connection). Instructions say to knock these out on the appropriate side.
However there is a hole in the rear of the cistern for rear access. This would suit as I can pass a flexible tap connector through it. This can emerge from some boxing in I have constructed against which the wc will be placed.
So - are there any cistern flush mechanisms which allow internal connection of the cold water feed inside the cistern? I cannot find one through searches, but I vaguely recall when installing a previous Fluidmaster that the instructions showed such a variant.
If one exists this would save tapping out the water inlet connection, which makes me rather nervous.
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