Beorum?
Long ago and far away, a woman at work had a deal with "junket" package arrangers...that is, those folks who made arrangements for the entire plane to be sold to some group who decided to go to... Norway or whatever.
The woman would carry her passport, money, and a spare suitcase with her, and made herself available to fill an empty seat on almost ANY flight they had...for 1/2 or 1/4 price, as I recall.
Might try to see if there is some sort of group travel deal going to the city you seek and call them saying you can do last-minute fill-in.
Good luck.