How to fairly deal with the slippiness of druids due to wild shape?

So there will be a lvl 5 druid joining my campaign and I would like to introduce them by having them held prisoner in a lizardfolk village.

Obviously this raises the question how rather simple lizardfolk would manage to keep someone captive for extended periods of time that can easily escape any kind of cage or restraints by wildshaping into a mouse, spider or similar. Therefore, I would like to introduce some simple kind of way for the lizardfolk to deal with this, without totally making the wild shape feature useless in the world for the druid and by that punish them for choosing a druid. However, I think that in a magical world, wild shaping seems like a rather common issue, so most people running a prison would probably have a way to deal with creatures trying to escape that way. Especially lizardfolk, since their shamans have the ability to turn into crocodiles.

My ideas so far:

1) A very tight-woven cage (or maybe insides lined with leather) with a constant guard post that checks on the druid regularly. However, this still seems rather unsafe.

2) Some kind of herb/drug that can be administered forcefully or with the prison meals that suppresses/numbs the druids connection to nature making him unable to wild shape. (Lizardfolk Shamans would probably know about such herbs). However, the existence of such a drug would have major implications for the entire world/future of the campaign.

3) Magic suppressing shackles, although I think that would be a very unusual item to have for lizardfolk living in the middle of a swamp with little contact to outsiders.

I am sure a lot of you have had to deal with this particular problem and any ideas/suggestions are welcome. Also, please tell me if I'm overthinking this.

PS: I also have spoken to the player, and they say they are fine with some way of controlling wild shape, as long as it doesn't become omnipresent or can be done quickly mid-combat by mundane creatures.