You already own this one.
Power
USB power supply and data cable
A phone charger and a USB cable power every board in this store. You very likely own both already.
The one catch: the cable must carry data, not just charge. Charge-only cables look identical and are the most common reason a board "will not flash."
Where to get one
These are searches, not endorsements. OAT sells nothing and earns nothing when you buy; the search term is the know-how.
How to pick a good one.
- Check the board's port before ordering a cable: the classic ESP32 usually wants micro-USB, the C3 and C6 want USB-C.
- If flashing does not detect the board, swap the cable first. It is almost always the cable.