Every time I visit my dentist I get a small sample tube of name-brand toothpaste. Each tube has enough to last at least a month if used sparingly. 

If that's too much to carry you could use up half the tube or more at home before you leave on a trip and/or save those partial tubes for future trips. I suppose you could transfer an even smaller amount into a small plastic container, but that seems too much work for little extra benefit.