So this is cool: Steve of Philofaxy recently took a Timer 21 (a French format that’s similar to the North American Trinote), a Filofax A5 hole-punch, and his A5 Filofax Pocket binder and voila! A brand new planner. Steve also discovered another format, the Timer 17, that’s compatible with the Personal Size Filofax. UPDATE: without extra hole punching!
Of course, his task was made easier by the fact that the Timers 21 and 17 already use a loose-leaf system. Here in North America, our planners are bound books and thus aren’t as easy to adapt to other covers. Still, we once heard from a woman who took apart an ABP/1 and put the pages in her FranklinCovey binder. When there’s a will, there’s a way!