level hubs use bolt on cogs and some folks have drilled bmx splined cogs to fit the disc side of single speed or front disc hubs.

skidding is not necessary in the velodrome, so it's not really a problem that most manufacturers care about...

edit: oh yeah, miche makes splined cogs that fit onto a splined carrier that screws on where the cog would go on a track hub. it would still cause stripping from skidding like underwear. underwhere?