I've designed a very handy wheel guard for the HU3 handset that allows you (or your focus puller) to place the handset down without bumping and changing the focus setting. It also protects against chipping and delaminating the premarked focus rings, as they tend to get mashed up easily at the edge. Black anodized aluminum, matches the HU3.
Just remove the two corresponding screws from the back of the HU3 and install with the two included screws. I've been using a prototype for about a year and whenever I'm not using my own HU3 I really do miss having that guard there under my fingers.
I've got some pics below. They're $45 (CAD) apiece, plus tax if you're in Canada. Shipping should be $4-6 anywhere in North America. For less than the cost of one replacement HU3 focus ring, you can protect all your rings.
Send me an email at email@example.com if you're interested in one.