To find Heart Scales, there is a random chance of getting one off of sand blocks and Luvdisc.
Second, the pokemon Luvdisc.
Upon catching this pokemon, there is a chance that it's holding a Heart Scale.
Now you may be wondering, why are most of my suggestions about Heart Scales?
Third, the Move Tutor.
If possible, he'll spawn anywhere and you'll be able to give him 1 heartscale in exchange for teaching one of your pokemon an old move or a move it can learn.
In addition to this, I would like to have more moves for pokemon like Draco Meteor, Volt Tackle, Extreme Speed and a bunch'a other moves.
Thanks for reading and I hope you support my ideas.