What are the rules for rebinding the suddenly freed arm of a bound prisoner to prevent them from attacking?

We are working on a scenario where a lich is bound and gagged but one hand gets free.

We are working on how to play out the scenario where relatively lower level PCs are trying to restrain the freed arm of the lich while it is attacking them with its Paralyzing Touch.

Are there any prior examples in adventures, guidance or rules around how the party would tie up the freed arm of a prisoner?

We looked at grappling but it appears the lich could still use its Paralyzing Touch because a grapple only grabs an opponent and doesn’t stop attacks.

We believe this question is different from this prior question as we are not asking about all the different ways to invoke the restraining condition, but rather specifically the prior art, guidance or rules around a specific scenario seen with tied prisoners.