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Easy; I'd use your current jack and add a pneunatic caster like this one: http://www.harborfreight.com/10-inch-...38944.html.
As all casters come with the standard flat square plate, depending on your current jack setup, you may need to buy or fabricate an adapter plate like this one: https://www.redtrailers.com/ShowItem....=CA5550301 to install it on the drop leg with a pin.