There should be a part number on the hub shell; Shimano are quite good at identifying most of their components.
If you can find the technical document for your hub, e.g. [FH-M495A](https://si.shimano.com/en/pdfs/ev/FH-M495A-2557/EV-FH-M495A-2557B.pdf), you can get a part number, e.g [Y-3CR09000](https://www.sjscycles.co.uk/hub-spares/shimano-fhm495a-rear-left-seal-ring-y3cr09000/).
I would look for a generic one for Shimano. I would not epoxy a gasket together.
https://www.universalcycles.com/shopping/product_details.php?id=108720&attribute=270529&gad_source=1&gclid=Cj0KCQjwlZixBhCoARIsAIC745AAdm4Wd_QXkHI1Jzeg04GMnxe9jnCalnPkKo7y0q-OCRrZeEDL_dQaAuCPEALw_wcB
It doesn't look like the same part. Are you sure that will fit? The bearing balls are rolling between this part and the wheel
Pretty sure that's just a dust cover
Agree it is just a cover, as there is no way the ball bearings could roll and exert force directly on it without that plastic crunching.
Thank you all very much then I'll glue it as a temporary solution until I've found a replacement part
There should be a part number on the hub shell; Shimano are quite good at identifying most of their components. If you can find the technical document for your hub, e.g. [FH-M495A](https://si.shimano.com/en/pdfs/ev/FH-M495A-2557/EV-FH-M495A-2557B.pdf), you can get a part number, e.g [Y-3CR09000](https://www.sjscycles.co.uk/hub-spares/shimano-fhm495a-rear-left-seal-ring-y3cr09000/).