have factor alloy wheels and the littel dime sized plug in the middle of 3 of my lug nust are missing.

does anyone knwo if these can be  bought or aquired somehow, sold by an after market source? The dealer says you need to buy the whole lug nut to get it and each lug nut costs $11.15 each.

Short of making it oneself any suggestions? Other than the midnight free parts place.