In a previous post I described an idea I had for a small, motorized caster. I took that design and made it. Here is a quick video showing my first build.
Here's what it looks like next to the passive VR shoe. You can see it's slightly shorter.
Here's what it looks like next to a regular shoe. I'm thinking I'll have one right under the heel as shown, two more right in front of it (so three under the heel forming a triangle), two more behind the ball of the foot, and two more in front of the ball of the foot.