Baggage help !!

I book one way reward tickets (using united miles) from New York to Singapore and Singapore to India with stopover in Singapore for 4 days. I called the airline about baggage allowance for my first destination I am allow to take 2 bags 50lb each, and for my second destination I am only allow to take 1 bag/20KG. I tried so many ways but united policy will not allow same ternary if you have stopover more then 24 hrs. I am looking for advice on how to take same weight in second flight? Anyone know how much it cost to take second bag from Singapore to India in Singapore airline? I was told that on airport they will tell me how much will it cost per bag? I guess they are thinking of weight? Any other alternate solution?

Thanks a bunch..