There used to be a Fedora equivalent called febootstrap, but it looks like it's mutated a bit since then: http://people.redhat.com/~rjones/supermin/
You may be able to work around it that way.
Out of interest, what machine are you using CentOS 6 on? I find 128mb kinda tight - although I've recently found a VPS provider who's managed to get Debian Jessie working in 96!