0 thru 9 Flipper Card Decks in various sizes make auction lotting a breeze. Big, bold black numbers are dye sub printed on durable aluminum material that will take repeated usages. Buy them and build your own holder to accommodate any number of digits you need.
Split rings make it easy to "flip" the number over to create a multi-digit lot.
NOTE: Size is of the overall card, NOT of the number.