How to add updates &extra applications to Mythbuntu Live USB?

[hhtmp88]

Dear all,

I would like to add:
* Ubuntu9.10 updates (recently there are 160 updates!)
* and some applications (e.g. 7-zip, gparted, clonezilla, etc)

to Mythbuntu Live USB?

so, how to do that?

Thanks for any kind of help!
Rgds,