This isn't the first third-party HTC EVO dock with an extra slot for charging a spare battery that we've seen, but the $39.99 "Supreme Desktop Charging Dock w. Spare Battery Slot" (as it's descriptively called) that you'd be able to buy if it wasn't out of stock at HTCPedia right now is probably the nicest and most compact of the bunch.
Although it can't accommodate an extended-battery-wearing EVO like Seidio's desktop cradle can and it doesn't have an HDMI port like the official EVO docking station does, it still looks like something that could feel right at home on your desk or nightstand. It comes with an AC adapter (required if you want to charge a standard-size spare battery) and a micro USB cable for charging/syncing, so you don't have to go out of your way to welcome it into your life. All it needs is your EVO.
More photos below.
There's also a version without the extra battery slot for $10 less. Unforutnately, it's also out of stock at the time of this writing.
Both docks were available when I checked on them last week, though, so you might want to keep an eye on the link below if you want to know when they're back in stock again.[HTCPedia]