I don't know much about mollasses its not my bag but from my understanding the reasoning for using it is to give the plant an increase in sugars and carbohydrates to give it an energy boost into producing bigger buds.
I would have thought that any natural product derived from sugar would have a similar effect to mollasses.
you can buy molasses at tesco, morrisons or any other big supermarket in the uk. ive bought it and used it on my last grow but didnt see much difference in the growth. i diluted it in boiling water, 1 x teaspoon per litre. hope this helps.