I haven't looked specifically but it should be one that supports USB PowerDelivery, Quickcharge is not the same and won't help. It should be capable of 15V output at 1.6A at least.
From the Surface power supply FAQ
Any charger that supplies ~29 watts or more will work well with the Surface Go.
After looking a bit for a charger I feel you cannot go wrong with Anker.
For a charger only... the Anker PowerPort II, 49.5W Wall Charger with Foldable Plug, One 30W Power Delivery Port.
Battery Pack ... boy there are lots of them that don't fit the bill. AFAIK you should have one with 15V output at up to 2A 30W (1.6A for 24W) lesser specs might still work but it will be slower and might not keep up while using the device and charging at the same time.
I found this RavPower unit that looks like it checks all the boxes.
Type-C Output: DC 5V/3A, 9V/2A, 15V/2A, 20V/1.5A https://www.amazon.com/dp/B01LRQDAEI/
