There are several jack type supports on the market, just search on them. I suggest you hold off for a bit, since you're new to the unit, you might get use to the motion after a while. But, if you have to have it motion free, you will trade that off for setup and take down exercises, storage of jacks (min of 2) base material under jack etc. You will need to crawl under it and find out the points of easy access are; at the rear hitch structure, and at the front chassis area.
Oh, by the way, buy some dry lube spray and lubricate all friction points, including the underside of the slide box on the slide, and check all the bolts, you might find they need to be tightened.