I can't give you an antibody, but there's a vital-stain of mitochondria with Janusgreen B (0,05% in Ringer). Cover the slide in a wet chamber for 10-20 min. Rinse in water and coverslip with aequous media.
Mitochondria should stain blue-green. The stain needs access to oxygen while staining.
I never did this stain personally. Reference in Romeis.
In Bancroft's the Altmann's technique for mitochondria is described. A stain with Anilin-acid fuchsin on Helly's-fixed paraffin sections.