Amazon has a 2-pack of Pentel EnerGel Deluxe RTX Liquid Gel Pens (0.7 mm) in black (https://www.amazon.com/dp/B001G9C6L0?tag=quackdeals-20) or blue (https://www.amazon.com/dp/B002VL6LOA?tag=quackdeals-20) for just $2.82 (originally $7.20). Free shipping with Prime or on $35+ orders when you sign up for Subscribe & Save (cancel anytime after your order ships).
(https://m.media-amazon.com/images/I/71OXNAKETtL._AC_SL1500_.jpg)