I have an idea for a new build and believe that this item exists but can't remember the name of it.
Two chests who share the same content space regardless of the distance between them. You can keep one of the chests at home; then take the other on the road. If you put an item in either of the chests, it can be accessed in both.
I'm planning on building a Wizard Item creation specialist as my back up character and want to invest in a 'magic shop'. Taking commissions and creating items for adventurer's in my down time. Facsimile's kept at the shop and the real items kept on my person or in an extra dimensional space such as with the Secret Chest spell. Requests (by exchanging notes) and delivery handled through the chest.
Did this item only exist in 3.5? Or is it in Pathfinder? Or did I dream it up? Is there a better way?
I believe the item you're looking for is the Ender Chest from minecraft.
That said, Ring Gates might be useful for your purpose, though they have a 100 mile distance limit.