Kevin Mellott has just released an stl file of a 3D printed cover for the Virtual Boy controller’s rear slot: https://www.virtual-boy.com/downloads/1043263/get/1043264
While this is a bit of a niche use, people who’ve consolized their Virtual Boy will most likely be powering it from the console and no longer from the controller. This 3D print will be a nice way to cover the power port and make the VB controller look a bit more like a true console controller.
…and if you’d like to see some of the best stuff the Virtual Boy community has to offer, check out this livestream from last year!: