I have a silk liner from babykind that I bought when Katie has awful rash. Never got to use it though as it got better once I'd ordered it, typical.
When her rash was bad I stopped using all liners, made cloeaning the poo a bit more tricky but seemed to help a bit. if the nappy is fleece lined I just put a booster over the top - like others said that's what the swaddlebees pockets do
Bamboo would be good cos of the anti-bacterial properties.
((hugs)) to you Shevi and to poor Zacharia, I hope it clears up soon, rashes are horrid