LUFA HID has a 2k bootsize and is USB HID compatible so no drivers are needed.
Using a modified version of teensy_loader_cli to flash firmware.

Compiling LUFA HID requires WinAVR/AVR Toolchain and an ISP to burn the bootloader.
Guide to setup WinAVR/AVR Toolchain.
Guide to using Teensy 2/Pro Micro as an ISP.

[b]Compiling LUFA HID bootloader and flashing to Pro Micro (on Windows)[/b]

http://www.fourwalledcubicle.com/LUFA.php
1) Download [url=http://www.github.com/abcminiuser/lufa/archive/LUFA-140302.zip]LUFA-140302.zip[/url] and extract.

2) Navigate to '<where you extracted lufa-140302.zip>\lufa-LUFA-140302\Bootloaders\HID\' and edit 'makefile'.  You'll need a text editor capable of correctly displaying unix formatted text files, [url=http://notepad-plus-plus.org/]Notepad++[/url] or [url=http://liquidninja.com/metapad/]Metapad[/u] will work.

Configuring LUFA HID for Pro Micro clone

Change
[code]MCU          = at90usb1287[/code]
To
[code]MCU          = atmega32u4[/code]

Change
[code]F_CPU        = 8000000[/code]
To
[code]F_CPU        = 16000000[/code]

Change
[code]
FLASH_SIZE_KB        := 128
BOOT_SECTION_SIZE_KB := 8
[/code]
To
[code]
FLASH_SIZE_KB        := 32
BOOT_SECTION_SIZE_KB := 2
[/code]

3) Compiling

 3a) Open a command line window.  Start Menu > Run > type cmd.exe in the box.

 3b) Navigate to '<where you extracted lufa-140302.zip>\lufa-LUFA-140302\Bootloaders\HID\'
 example of what you type in the cmd window:
[code]<drive-letter where it's extracted>:
CD '<where you extracted lufa-140302.zip>\lufa-LUFA-140302\Bootloaders\HID\'
[/code]

3c) 'make clean' then 'make'

3d) If everything compiled correctly with no errors, 'BootloaderHID.hex' is the bootloader you seek.

4) Configuring the Pro Micro clone's fuses and burning the bootloader