I just got my Ninebot S, and I know what you mean about the lack of a valve in the hose. At the suggestion of my brother, who's had a miniPRO for several years, I just ordered this on Amazon - Aiskki Digital Cordless Inflator, Portable Tire Hand Held Vehicle-Mounted Compressor Pump,12V DC 150PSI for Car, Ball, Air Cushion
"Automatic Inflation: Only need to set the required pressure value, the air pump will automatically inflate, and automatically stop when the set value is reached."
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