Microsoft Surface Headphones 2 - Matte Black with significant stock from what seems like a reputable seller.
Alternatively to those who want to buy from Microsoft themselves, they're listed at $319 from Microsoft Ebay
From Microsoft's listing;
The next generation of Surface Headphones
Experience your favourite music and programmes like never before. Designed for all-day comfort, improved sound quality and more battery life, Surface Headphones 2 features voice, touch and fingertip controls with 13 levels of active noise cancellation. Now available in Light Grey and Matte Black.
Turn it up, tune it out
Experience your music, programmes and calls like never before with spectacular Omnisonic sound and adjustable noise cancellation.
Designed for comfort and control
Listen all day with soft, lightweight and comfortable ear pads. Use touch, tap or voice to skip tracks, answer and end calls, and get hands-free assistance. Your music even pauses when you take off Surface Headphones 2 and resumes when you put them back on.
Get things done with voice
Use touch and voice to play music, make calls, and get answers to questions from your preferred digital assistant. Use voice dictation for Word, Outlook, and more in Microsoft 365* (subscription required).
Length: 204 mm (8.03”)
Width: 195 mm (7.68”)
Depth: 48 mm (1.89”)
Colour: Light Grey
Frequency response:20 – 20kHz
Up to 30 dB for active noise cancellation
Up to 40 dB for passive noise cancellation
Speaker:40 mm Free Edge driver
Sound pressure level output:
Up to 115 dB (1kHz, 1Vrms via cable connector with power on)
Up to 115 dB (1kHz, 0dBFS over Bluetooth® connection)
Charging: Full charge in less than 2 hours
Battery Life: Up to 18.5 hours of music listening time or up to 15 hours of voice calling on Microsoft Teams
USB cord length: 1.5 m
Audio cable length: 1.2 m
3.5 mm audio connector
Compatibility: Windows 10 or later, Android 4.4 or later, iOS9 or later, Bluetooth 4.1/4.2 Buttons/controls: Power button, Mute button, Volume dial (right ear), Noise Cancellation dial (left ear)
What’s in the box:
Surface Headphones 2
Quick start guide
Safety and warranty documents
Warranty:1-year limited hardware warranty