I have purchased leather leftover from some other upholstery business, nearly full hides for not a lot of money.
Plan to use the original seat cover as a pattern for a new leather one, and or adjust a little as necessary. I also have heavy duty sewing machines and looking forward to the project when time allows.
There is very little stitching on the original seat covers, you could even do it by hand if you were determined to.
Or hire the sewing if you don't have the equipment, even that wouldn't be expensive.
Or hire the whole thing, materials and all, still I bet not cost prohibitive for the original style of seat cover.