Amazon has countersink drill bits set for $7.49 after 50% off coupon on page (YMMV)
- COMOWARE Countersink Drill Bit Set- 7 Pcs Counter Sinker Drill Bits for Wood, Quick Change, 1/4” Hex Shank, High Speed Steel, 5 Flute 90 Degree Center Punch Tool, 1/4”-3/4”
- COMOWARE Countersink Drill Bits Set- 7Pcs Counter Sink Bit for Wood High Speed Steel, Woodworking Carpentry Reamer With 1 Free Hex Key Wrench