Seconding the Angelus leather paints. The reason for the chipping is because regular sprau paint isn't mean to be applied to surfaces that are going to flex. Leather paint is, which is why it is better to use. With leather paint, you don't need to prime or seal, although using their sealer will help with the life of the paint on the leather.
From my experience, even after a good day of walking, if you even have any wear on the paint, it will be minimal. After an entire weekend in a pair of painted boots, the creases in the toe area needed a little touching up, but it wasn't bad. I did a lot of crouching and moving around in them, and I didn't seal the paint, so I wasn't surprised.
I don't have any close-ups of my painted boots, but here's a picture of them:
I painted both the beige and the white (except for the the top white part, which is fabric).
I've since painted another pair of boots with the same stuff, and had equally good results. I've used it for painting leather belts too, when I needed different materials to match in color.
I have to warn you though - since you already spray painted the boots, the leather paint won't work as it should unless you get the spray paint off first. The leather paint needs to be applied directly onto the boot material, not on top of a layer of paint that is going to chip. Unfortunately, I'm not sure of the best way to remove spray paint from leather, but I'm sure there's a way. Hopefully someone else can chime in on that.