Maybe find something fun and crafty, or productive around your place, to do with your hands while practicing breathing exercising that mimic the same breath work you'd be doing while smoking?
I remember the 4-4-4-4 breaths reminding me of smoking a bowl, you breathe in through your nose while counting to 4, hold it while counting to 4, exhale gently through your mouth while counting to 4, and then hold that space while counting to 4, rinse and repeat often. Increasing the count as you get more used to doing it.
It reminded me of taking a hit off a bowl or a joint, minus the smoke, but I discovered that oxygenating my cells via the breath work also felt good, not exactly like taking a hit, of course, but close enough to satisfy me, and so much healthier. Win/win. Now it's a regular part of each day, multiple times a day.