Bootable USB

We have a Ubuntu server running TFTP and PXE and it launches Clonezillia. Works great. I PXE boot, get DHCP, connect to the server, choose Clonezillia from the menu, and I am off to the races.

Behind the scene, it runs this command :
LABEL Clonezilla-live KERNEL tftp://192.80.16.40/images/clonezillia/vmlinuz

For many reasons, I have a subnet that has DHCP, but I cant have the PXE option point to the Ubuntu image server.

How do I go about getting a bootable USB drive, that will boot, get a DHCP address, and offer the menu so that I can boot the Clonezillia image using:

LABEL Clonezilla-live KERNEL tftp://10.70.160.70/images/clonezillia/vmlinuz

Thanks.