Google Flights allows flexible destination searches when an origin is specified. Is there any way to do the reverse: a flexible origin search with a specified destination? For instance, I know the city I want to fly to, but am willing to position, and therefore want to scan many departure points to find the cheapest option? (Or any alternative service which allows this? I am a Matrix power user, but I want to scan more origins than that really allows... and I hate that if the query is to complex it will just return partial results with no indication anything went wrong...)