It's a bummer you say that Pomodoro timers don't work for you. I work in technical writing, and the Pomodoro system is ideal for keeping me on track, even when I'm testing a system (which bores me to death, let alone writing the documentation for it). Knowing that I have a short break after the end of a sprint's worth of work keeps me motivated... when I remember to use the Pomodoro apps on my phone and Mac.
I set up a great system in Apple Reminders for my to-dos and lists. It's a powerful tool if you use Apple products, more than just mere reminders.
Are you medicated? That helped me a ton in more ways than I can count. But I've never tried body doubling, since I've worked solo from home for the last seven years. Background noise is also helpful to me, such as Reddit videos in the background (especially r/NiceGuys compilations). Music, too. Podcasts and audiobooks less so because I become more focused on listening than being productive.