Accupro - 1/2 Inch Shank Diameter Straight Shank Micro Drill Chuck Adapter and Chuck - 41868365 - MSC Industrial Supply
Bestgle 1/2-20UNF Mount 1.5-13mm Capacity Key Drill Chuck for Air Impact Wrench Converter Conversion Tool with Chuck Key and 1/2 inch Socket Square Female Adapter - Amazon.com
Drill Chuck, 1/2" with R8 Arbor 1396 - LittleMachineShop.com
1/2" Jacobs Keyed Drill Chuck On 1/2" Spindle Adapter fits 1/2" Motor Shaft New | eBay
Jacobs Chuck Jacobs 1/2-In Dr. Keyless Chuck Dual Sleeve in the Drill Parts & Attachments department at Lowes.com