This is one of those tools that a tinkerer would appreciate. An absolute life saver when you have lots of things to fix. The mini version is compact and has less torque and is suitable for things like toys, watches, laptops and small electronics that has smaller screws.

Supplies

N20 motor with gear reduction, am using the 100rpm version better torque.
500 mah battery
A cheap multi tool screwdriver (rubber handle removed)
3 way switch
Power IC from a power bank
3mm LED
3mm to 5mm shaft coupler
A push button

Step 1: Finding a Suitable Body

These cheap power banks are easy to find, I had a couple lying around, we only need the body and the power module from them. Since this is a mini screwdriver anything small like a tube or so would work, in fact you can use other shapes if you can fit the components nice and sturdy.

For the body that I had It already has a led, a button that turns on the LED and the micro usb input to charge the battery, we don't need the USB female socket which was originally used to charge other devices so that was removed and in place of it I added the 3-way switch which fits in perfectly with the help of hot glue.

I had to do a couple of holes for the button, the led and the motor shaft.

Step 2: Connections

By default, the power module that came with the power bank had an onboard LED which I leveraged it by desoldering from the board and placing it elsewhere with the help of longer wires. If you have a power bank that does not have built in LED, then you can simply connect an LED to the same terminals as the motor and it should work when the motor spins.

A 3-way switch works as shown in the picture, it basically reverses the motor direction when the switch moves from position 1 to position 3, Position 2 is the OFF mode.

Step 3: Getting Things Together

I mostly used hot glue for the components but used instant glue to fix the motor to the body for added strength. The body is essentially 2 parts and they were slightly loose, so I wound it with black tape.

Step 4: Testing

It works well when used for the right purposes. You can make it much sturdier if the motor is attached to the body by having screws in its intended positions.

It has been about 6 months since I made this product and has been working flawlessly and has been extremely helpful for my projects.