I bought mine the other day from Amazon while it was a daily deal, Miboxer C4 Plus.
I opted for the Miboxer C4 Upgrade and it fits a 21700 with about 8mm to spare so easy to take in and out. Price was $26 on Amazon after clipping the $4 coupon. Can be powered either with a 12vdc power supply with 5.5x 2.1mm plug or with the included AC cord. AC cord comes with either US or EU type depending on where you live. Shown in pic is with it powered via 12vdc.
Picture is with the Sofirn 21700 that came with the C8F flashlight. Red cell is 18650 GA
