Here is the instructable of an EDC key organizer combined with a 1/4" bit holder.

Supplies

60 mm long 1/4" bit holder extension - 1 piece
Bicycle chain outer links - 2 pieces
Nut + bolt - 1 set
25 mm metal D-ring - 1 piece
Rubber washers - 4 pieces (2 of them are optional)
1/4" bit of your choice

Step 1: Drilling the Bit Holder Extension

Drill a hole in the shaft of the holder so that D-ring can pass through it. I used a diamond bur attached to a dentist's high-speed handpiece.

Step 2: Attaching the Bike Chain Links and D-ring

Slightly bend the D-ring to create space for the bit holder extension and chain links and pass them through the D-ring. Bit holder extension should be in between the chain links. Then, reposition the open ends of the D-ring head-to-head so that links and bit holder extension would not come off.

Step 3: Securing the Bit Holder Extension

Pass the longer part of the bit holder through the rubber washer. Take one side of the rubber and pass it over the short end of the bit holder so that the rubber prevents lateral movement of the bit holder and keeps it centered in the D-ring.

Step 4: Attaching the Keys

Pass the bolt through the free end of one chain link and add your keys. Then feed the bolt through the other chain link. Use the rubber washer and nut to secure the bolt.

Step 5: Optional: Rubber Stoppers

Add 2 rubber washers to fill the narrow neck of the bit holder. These stoppers allow easy and quick positioning of the additional tool for increased leverage.