We've always liked a good cup of coffee here at VO, and since we also like to travel we have been trying to find a coffee setup to take with us on our tours and day trips. The Soto coffee maker is a great little filter holder that folds down small to fit into any handlebar bag or seat bag, and it's light enough that it won't be noticed.
The ingenious design of this filter means that it won't collapse under the weight of water and wet grounds. It is made like a spring, so the default is that it is open. It uses the three base prongs to hold it shut for traveling.
The base pops out to 4.5 inches by 4.1 inches, so it should fit most mugs out there.
Made of stainless steel coil, this 45g filter holder comes with a mesh carrying bag and 10 cone filters. Additional #2 filters can be found at your local grocery store.