This seems unsolvable without new compostable or otherwise easily processed plastics.

At our university a bioplastic "nonoilen" was developed that can be made from waste biomass (PLA + polyhdroxybutyrate formula) and compostable without any toxic residues. So far, like most "compostable" plastic, it requires industrial composter with temperatures over 50°C, but further improvements are being developed.

https://www.plasticsinsight.com/stu-team-develops-second-gen...

Toothbrush manufacture is planned (Slovak language, sorry). Hope it works out: https://aprilmagazin.curaprox.com/prve-curaprox-kefky-z-biop...