ORIGINAL: sabotloader
Knight did and I think still does make sabots (some sabots). Usually Knight sabot had a smooth cup and a wide space between petals. Harvesters and MMP usually have a very tight space petal to petal.
I honestly do not knowhow many companies make sabots....
MMP makes Knights. The other company is Harvester. I think Hornady makes some also but I am not sure on this.