Back in the day the David Allen Company would sell physical products like planners, file folder systems, inboxes, etc.  One of the last things I bought from them before they stopped selling physical products was their ORANGE mesh travel folder system.

It consists of the following folders:

• IN – Your mobile inbox just like in your office at home and work.
• TO OFFICE – Items that need to get back to your office.
• TO HOME – Items that need to get back to your home.
• ACTION SUPPORT – Anything that you currently physically need to complete PROJECTS or NEXT ACTIONS.
• WAITING FOR SUPPORT – Physical items or reminder notes of items you are waiting for someone else to complete.
• READ/REVIEW – Items you want to read or review while being mobile.

Based on my needs, I have added two additional folders:

• REFERENCES – Key references I want to have with me while mobile. For instance physical copies of the GTD Mastering Workflow Series Methodology Guides.
• CALENDARS/CONTRACTS – Print out of key yearly work and family/school calendars.  And then a select list of phone numbers and emails I might need to reference if I don't have my phone.

These could be duplicated today with a good label printer and quality plastic file folders.

You can still get a good amount of GTD material in electronic format like planner templates, methodology guides, workflow map, etc…