This mod adds craftable chests, that can be taken on the go to store your items, and can be upgraded to higher tiers to store even more. These chests seemlessly fit into vanilla minecraft aswell.
It also adds an item called a "Pocket Dimension" which is a portable nether portal.
NOTE: Keep in mind that upgrading a chest will remove its contents, so make sure to take everything out of the chest BEFORE upgrading it.