1.You shall add dried Orange Peels powder and dried Avaram flower petals powder too.
2.If you know a mill to grind bath powders, do get the solids(unground) with the same mentioned measures, dry them and grind it in the mill. I usually do not opt for store bought powders but this is an exception as it is for external application only ;)
3.Solids and powders will be available in Ayurvedic/Herbal Medical shops(Naatu Marundhu Kadai)
4.Just have the required quantity for a month in an air-tight container and use it daily. Store the rest in freezer and take the next batch when the first is over. The one in freezer keeps well for 6 months to 1 year.