I am trying to find teething pads like this for my carrier which is Lillebaby brand. It is easy to find bibs like these to fit brands like Ergobaby and Tula. But for other brands including evenflo you probably have to find someone to custom make it for you. I am contacting someone based in Australia to make for me. She is called Babyanicka, you can search for her on Facebook. Most of the accessories makers i reach out to based in Singapore do not make for the uncommon brands and they usually have too many orders on hand for Tula carriers that they hardly will have time to custom make for other brands. You can still reach out to them to enquire though. One of them is www.quirkibabies.sg alternatively I let my gal wear a bib when she is facing out in my carrier.
Mummy, if you can't find the bib, perhaps you want to contact one of the local accessories makers to custom make one for you? Try Mamacat. She makes super nice stuff!