The Nexus 7 dock is back up for pre-order at another retailer after making an appearance in a holiday video and selling out of the pre-order at another online store late last week.

Excalibur PC lists the Nexus 7 dock as backordered, but shoppers can add it to their cart and pre-order the dock for $39.99 plus $7 shipping, as spotted by Droid-Life.

The Nexus 7 dock includes a Micro USB charging port and a 3.5mm out connection to connect to a pair of headphones or speakers. The dock connects to the Nexus 7 through four small metal contact points on the edge of the tablet.

We’ve heard the Nexus 7 dock would be available in December for some time, but so far it is only up for pre-order at third-party retailers like B&H and Excalibur PC. We expect at some point it will join the rest fo the nexus 7 accessories in the Google Play store.

Excalibur estimates the Nexus 7 dock will ship by January 6, 2013, a week after the December 30th estimate from B&H photo. At the time of this writing the Nexus 7 dock is still available to pre-order by clicking on the backorder button, though it’s likely the dock will sell out just as fast as it did at B&H photo.

The dock will charge the Nexus 7 through these POGO pins, but it doesn’t give the Nexus 7 the ability to do video out to a monitor or HDTV.

The Nexus 7 dock also appeared in an Android holiday video alongside a Nexus 10 dock. Neither dock is officially available yet.

Nexus 7 owners that miss out on the pre-order may be in for a long wait as Google is notoriously slow to get devices and accessories back in stock for the Nexus 4 and Nexus 7.