Found at my local store. YMMV, but Brickseek shows it discounted and in-stock at most of the stores around me. Good luck!
Lowe’s has DEWALT 50-ft Spool 0.08-in Trimmer Line marked down to $1.99 (reg. $8.58) w/ free in-store pickup – YMMV.
SKU: 50329517
Brickseek: https://brickseek.com/lowes-inven…u=50329