Is the number of animals killed driven by food consumption, with the leather industry using excess, leftover product that is not eaten? If so, I wouldn't personally feel very guilty about using a small volume of leather goods; I'd see it more like the native americans viewed avoidance of waste.
If leather consumption were a significant factor in the rate of animal consumption, I would be more careful to avoid leather goods. Also, if I developed an emotional aversion to seeing animal products, I would be careful to avoid them. Personally, I'm on the edge of going vegetarian, having cut down my meat consumption to a couple of meals a week. My main motivation is health, but environmental responsibility and ethics play a role as well.