The easy option would be to splice directly into the dipped beam circuit as you suggested and as it draws 60/55w anyway then it won't be much extra load, I have done similar bodges on other bikes over the years with no issues, the more professional option would be the relay and take the live feed from the dipped beam circuit, I have also tried that method on my gen1 to wire in USB power source to the brake light circuit, although it worked well and was the more thorough option I really didn't like the extra wiring under the seat because of the additional fiddling when doing other maintenance tasks, the only thing I wouldn't recommend is going direct to the battery, if it were me I'd go for the easy option 😉