Amazon has the well-reviewed 12-Pack Pentel EnerGel RTX Medium Point 0.7mm Retractable Liquid Gel Pens (Assorted Colors) for $13 - 5% off with Subscribe & Save (can cancel anytime) = $12 with free shipping on $35+ or with Prime (extra 10% off for 5+ subscribe and save orders). Office Depot has it for $1 more.