First you need o get those bushings out. Try using a small screwdriver against the back side of the bushing (CAREFULLY!!). You may need to give it a tap with something. They should push right out.
Next, measure the diameter of the bushings. They will be either 9 or 10mm.
Third, order a set of tuning pegs from somewhere like stewmac.com with the same bushing size.
Finally, I don't see why you'd want locking tuners on an acoustic. They are designed for use with vibrato units like on the Fender Stratocaster. Acoustics don't slip out that much.