This e-nose in general interesting, do anyone know any sensors that are currently commercially available to prototype these things?

KIT had a project on this (Project KAMINA) which looks like it is also cited in the linked paper.

They had a spin off SMELLDECT GmbH which sells a kit but not exactly a order from DigiKey thing. I imagine you will need to send an RFQ and go through the motions with their sales team.