Amazon.com: SoundOriginal 2pcs Brushless DC Cooling Fan 24V 0.06A 40mm x 40mm x10mm Speed 6800 RPM Fans for 3D Printer Humidifier Aromatherapy and Other Small Appliances Series Repair Replacement (Black 24V) :
Noctua 40x40x10mm 5 Volt Fan NF-A4x10 – Coolerguys
Amazon.com: Noctua NF-A14 iPPC-24V-2000 IP67 PWM, Heavy Duty Cooling Fan, 4-Pin, 2000 RPM, 24V Version (140mm, Black) : Electronics