[CentOS] 'initrd' image of CentOS (domU) on Ubuntu (dom0)

Hello,
 
What is the best way to get the xen enabled CentOS 5.2
vmlinuz and initrd images for use as a guest domain
(domU) on Ubuntu host domain (dom0). 

Is there a site where these are available? I am hoping
that I could use the vmlinuz from the latest kernel
rpm, if I go that route, how could I generate the
initrd image given that my host is Ubuntu?

These are for use with post install of domU, which
is setup using xen-create-image.

Thanks