if you replace the home button with a 3rd party, you will lose Touch ID capability. the only way to retain Touch ID is to have Apple do the repair and it costs (so i'm told) upwards of $300.
you can DIY the replacement. the 7, 7+, 8, 8+ and SE2020 all use the same home button.
yes you can get them on ebay, but i've stopped getting parts from there and switched to regular vendors because of better post sales support.
ifixit sells buttons - [product|IF332-079]
so does mobile sentrix - https://www.mobilesentrix.com/home-button-solution-for-iphone-7-7-plus-8-8-plus-se-2020
i've had a lot better success with the JC brand (mobile sentrix) than i have with the HX (ifixit) or YF (ebay) buttons, but that could just be my own experiences