I am assuming you have an ISO image that is 4.37GB in size but your flash drive is not large enough to carry it
The simplest solution is to get a larger flash drive
But of course, this is not what you want. So you may want to use WINRAR to compress the ISO into a rar file
I assume you would like to keep the 1:1 backup intact so you do not want any scrubbing
but raring without scrubbing may only save you a few hundred bytes, so you end up with a 4.xx GB rar file
even worst is that when you are going to burn the ISO image, you need to decompress it from the rar file, which requires nearly 2X harddisk space...
but hey, you do make the ISO smaller in this way
And then you mentioned about gamma, which only reads DVD with a proper 4.37GB ISO burned onto it
gamma does not read your flash drive nor rar file on a DVD