There is a proper rubber for the job, not sure if conveyor belting would be strong enough unless it was very thick, 1/2" minimum. Around here we always used the tread of an old tyre, a light truck or van tyre works well, just cut off the sidewall & flatten out the tread into a strip.
One of my farming friends cut a big tractor tyre up to top to bottom then cut each half circle along the middle of the tread line make four scrapers and bolt them to the scraper frame as needed use big 3 x 1/4 washers on the rubber side and nylock nuts to secure it to the frame . Being crescent shaped it's a very effective scraper