This is what I went with. They are heavy duty metal stands that were used on a loading dock. I got mine off of Craigslist. But they do sell them online. The new ones that can handle the weight are very expensive! Mine used were $700. But would have cost twice that amount new. Like some have said, you don't want them too tall. Mine are 8.5 inches tall and just fit under the motorhome.
You could also try stacking lumber to make a sturdy stand. There are instructional videos on how to do that on YouTube.