Sunvalleytek via Amazon [amazon.com]
has the RAVPower 26800 mAh Type C Portable Charger + 30W USB C AC Charger for $69.99 - $22.00 = $47.99 with promo code PB058RAV at checkout. Standard shipping is free.
Based on recent tests, this power bank appears to be the best out there for Nintendo Switch and is comparable to the actual wall charger due to the PD feature supplying the needed juice that Switch needs. Standard USB-C 5V/3A only nets you about 8% per hour while playing zelda handheld.