For this week only, Best Buy is discounting the official ASUS ROG Ally Charger Dock by over 50% off. It's normally $65, but you can get it today for $29.99. Note only does it work for the ASUS ROG Ally, users have reported that it works with the Steam Deck as well. If you want a traditional docking station style charger, then Anker has a model that's still much cheaper than the official Steam Deck one.
ASUS ROG Ally Charger Dock for $29.99
The ASUS ROG Ally Charger Dock is an extremely handy accessory if you want to connect your ROG Ally to an external monitor and use peripherals. Although a basic charger is included with the ASUS ROG Ally, no docking station is supplied. The charger dock looks very similar to a basic brick style charger, but with three ports instead of one. The USB Type-C output supports up to 60W of Power Delivery, which is close to the maximum charging rate of the ROG Ally. There's also a USB Type-A port for a keyboard, mouse, or USB storage, and a 4K @ 60Hz HDMI 2.0 port for an external TV or monitor.
Also compatible with Steam Deck
You can also use this dock to charge your Steam Deck and output its video to a bigger monitor or TV. The Steam Deck accepts up to 38W of USB Type-C of Power Delivery, so it's well within the 60W maximum output of the charger. The official Steam Deck docking station costs $79, so you'll save quite a bit by getting the ASUS charger instead. If you really want a charger dock that also functions as a stand for your Steam Deck, then the deal below might interest you more.
Anker 6-in-1 USB Hub for ROG Ally and Steam Deck for $39
Anker also has its own dock charger for both the ASUS ROG Ally and Steam Deck. It's currently on sale for $39.99. This model has a slot that lets you slide in your Steam Deck or ROG Ally console. It has a lot more features like a USB Type-C port with 100W of Power Delivery, a 1Gbps ethernet port, two USB Type-A 5Gbps ports instead of one, a second USB Type-C 5Gbps port, and a 4K HDMI 2.0 port. There's also an integrated USB Type-C cable with 90 degree connector that plugs right into the top of your console. The Anker docking station is obviously bigger than the ASUS charger but it also has better build quality with its entire shell made out of aluminum. The only caveat is that the slot is mated for a bare Steam Deck or ROG Ally; if you have a case, you might need to remove it in order for it to fit.
If you're looking for more accessories, check out the best Steam Deck deals.