Redhots are made for Knight by Barnes. They probably come with the MMP HPH-24 sabot. The picture though looks like a MMP 3P-EZ which is even smaller loaded OD.

This is the old bullet but Speer changed it slightly. Now the copper covers most of the lead or so ive read. Speer part#4481
https://www.natchezss.com/speer-jack...jhp-50-ct.html

You can get them at MidwayUSA and Grafs. I like Grafs because they are flat rate $7.95 shipping and they got good sabot pricing.

Speer 260gr https://www.grafs.com/retail/catalog...roductId/17363
I would try this sabot since its virtually the same OD as the HPH-24 and its cheap. https://www.grafs.com/retail/catalog...productId/5481

I shoot that same sabot in one of my customs. They will handle any load you will be able to shoot. If you want the MMP sabot just go directly to MMP its under the high pressure sabot section called HPH-24