Plastic free tea bags are a product that really shouldn't have to exist. But they do, because many tea brands use polypropylene, a type of plastic, to seal the tea into the bag.
This is so widespread, in fact, that Clipper was the first brand to create an 'off the shelf' plastic free teabag as recently as 2018.
Tetley, PG Tips, Co-Op, Yorkshire Tea and Lidl are among the brands still using plastic seals, although some are planning to phase it out.
Rather than creating yet more pollution, simply use your reusable cotton tea bag to brew loose leaf tea. Pop through the wash after making your cuppa and you're good to go. More compact than a tea strainer, and compostable at the end of its usable life.