This handy snippet of regular expression in PHP comes in handy for modifying the output of get_the_post_thumbnail.
I used it like this:
$url_large = esc_url( get_the_post_thumbnail_url( $product_id, 'large' ) );
$attr = [
"class" => "xzoom-" . $product_id,
"xoriginal" => $url_large,
"loading" => "lazy"
];
$thumbnail = get_the_post_thumbnail( $product_id, 'thumbnail', $attr );
// Strip out srcset and sizes atttributes.
$thumbnail = preg_replace( '/(srcset|sizes)="[^"]*"/', '', $thumbnail );
echo $thumbnail;