MMP makes a .36 caliber sabot that fits .311 - .314 bullets. MMP recommends that they be used with a 60 -90 grain bullet, compared to a .350 round ball which weighs 65 grains.
There's also .36 Maxiballs which TC made the molds for. A seller on Auction Arms named blkpwdrsls seems to list them for sale there all of the time.
Some good accuracy results for the .36 Maxiball are mentioned in this thread: