Good luck finding a site that is helpful for you. The majority of people would like to find affordable business class direct flights, so where there is demand, price is usually high.

Cheap business class will normally require a number of the following:
- flexible dates
- flexible start / end locations
- flexible routing
- flexible carrier
- flexible carrier attitude towards errors

if you have a number of air miles, you can Google the best redemption options for that programme and a number of sites will recommend best redemptions. Buying points is rarely a saving.