Extension Rod Collet Chuck C10-ER16A-100L (C10 = 10mm shank, A = Nut style, 100L = Length of Shank) $3.16 each when I ordered.
https://www.aliexpress.us/item/3256801499055632.html?spm=a2g0o.order_list.order_list_main.5.51c31802Rgtc3i&gatewayAdapt=glo2usa
ER16 -10pcs $11.82 for set when I ordered
https://www.aliexpress.us/item/3256806725203541.html?spm=a2g0o.order_list.order_list_main.11.51c31802Rgtc3i&gatewayAdapt=glo2usa
Drills and Cutters.com $25.00 with shipping https://drillsandcutters.com/?gad_source=1&gclid=CjwKCAiA9bq6BhAKEiwAH6bqoFgRhs0lzhwe1U25zzyF4zy_Vxt5jM_mOVBO3SRtwROBtRRblif_VhoCylkQAvD_BwE
DWDST34 $0.54 USD #6-32 67% thread depth
DWDST29 $0.63 USD #8-32 69%
DWDST23 $0.77 USD #10-24 66%
DWDST20 $0.81 USD #10-32 71%
DWDST5 $1.10 USD 1/4”-20 69%
DWDSTG $1.72 USD 5/16”-18 71%
DWDSTO $2.18 USD 3/8”-16 73%
Total cost with shipping approx. $75.00
Thread depth chart: http://theoreticalmachinist.com/PopUps/TapDrillSizePopUp.aspx
Thread depth chart #2 https://drive.google.com/file/d/1LbCv5-J_uXeySNdSl6vHpZOuMhIONh9q/view?usp=sharing
Guided Tap Handle (used in video): https://youtu.be/sC9lWrQeNX0