If my read is right, you're talking about VR trackers?
HTC take the lead with the Vive trackers (currently only VR tracker), just launching the 3.0 devices. An upcoming alternative is likely to come called Tundra from a kickstarter that's about to go live. Those will be cheaper than the HTC trackers, with a potential summer availability.
Worth pointing out though, you'll need a steam compatible headset to use all trackers currently available, and i think the base station tracking system? and wireless usb dongles.