No, was looking for something like that but did not find it 2+ years ago.
Ended up with a slightly upward angled raised stand, essentially a small A frame with 2 outfolding Amp holding arms.
Pretty solid, with adjustable height. Forgot model/brand, but can check when I get home tonight.
While it would be inconvenient to push the HD500 under the A frame from the side, I found that leaning it on the 2 arms of the forward facing A frames gets it sufficiently out of the way and almost completely under the Amp.
If you can find a wide enough A frame you could potentially just push it (flat) between the A frame legs. Probably not much better though because of the rubber feet on the HD500 as you'd have to pick it up anyway unless you get some wheels for it ;-)