SSRS max upload size limitations
From my understanding, This is a restriction specified on the server piece. So you would have to modify it's web.config to change the max upload size.  I'm not aware, although I could be wrong, of a way to change this setting through options within the reporting services management site.

You could ask your client to temporarily modify this.  Or ask them if they would be able to increase the max upload limit to 10mb.