Remember if you want to use SWUs to UG you'll need W or above fares.

If you narrow down the destinations you can use ITA with this sort of search:

sfo;sjc;oak::ua+ / f bc=W | bc=v
hkg;sin::ua+ / f bc=w | bc=v

the ua+ narrows the search to UA flights and the / f bc=w | bc=v selects only W and V fares which are most common/cheapest for int'l flights that can support an SWU.

Given your times, I suspect you're best bet will be flying on the 25th