"Would be nice to have more tools to get into that state."
I'm with you on this sentiment. But I feel like the point of a lot of meditative and yogic practice is to give us those tools. At the very least, that practice has made me feel that the process is learn-able and repeat-able.
I also agree that one issue is our narrow fields of endeavor. I play perform music, ride mountain bike trails, write, program... all of these will allow me to get into a flow state in one way or another. These flow states are all similar, but require different triggers and processes.
What's been helpful to me is recognizing that ritual and paying close attention to how / what I am thinking while I prepare and practice these things all have similar modes.
In the last 6 months I've started doing a lot more yoga, and the ritualistic nature of the practice has made that mental process a lot easier to observe. So now I try and develop patterns in my practices: specific singing exercises, a specific piano warmup, always having the same process for kitting out and checking out the bike before a ride, trying to keep a similar schedule and order for my workday, etc.
As to your comment about addiction, I've been doing a daily bit of kudalini yoga for the last couple of months and although I am not sure of the mechanism it evokes a psychedelic response in me (low-intensity visual hallucinations). Putting aside the short-lived nature of that response, so far it's reminded me of the patterns of addiction around those kinds of drugs: a) unless you do something really too much, these aren't bad results, and b) when there are bad results it's very easy to just say "clearly the aliens telling me to stop are right, and I don't need to keep doing these kinds of things to my brain" and move on to different mental exercises ;) . It's not like the times in my life when I was drinking heavily out of a sense that it was a "good idea" (tm), when in fact I was really being disfunctional.