Is there any form of pre-boot encryption for USB drives available?

I am aware that there is pre-boot encryption for drives holding an operating system, but, I could not locate or create a pre-boot encryption method onto a several USB drives that I have customized with bootable media to my daily tasks.

The problem I have is that there are times where I lose my USB, even with a big block attached to it. Other times, I forget to unplug it from the machine and go looking for it for minutes to hours even.

I wanted to know if I could put pre-boot encryption somehow on USB drives that act like boot CDs to prevent any customized batches of files from becoming compromised?


1) Is there any Open-source or Buy-now software available that can make any USB flash drive have pre-boot encryption before booting into a boot cd such as WinPE or Mini Windows 7?

2) Is there any other form of password-protection or encryption available that I can use for USB flash drives that act like boot cds?

I'm open to any ideas / methods.