The OFUG screwing a provider moment that is seared in memory from my youth was in 'Joe', starring Peter Boyle, from 1970. He wasn't really that old at the time, 40 I think, but fat and ugly he was. Or what about Taxi. Okay, not fat and not really all that old, but pretty ugly.
Also, any number of gangster movies have shown ugly, fat gangsters screwing providers in greater and lesser detail.
Now, if you had suggested a dearth of SYMPATHETIC portrayals of OFUG hobbyists, I'd have no quarrel.
But I think it's coming. As the baby boom ages there are an increasing number of old men who want to see their dreams of sex appeal lived out on the big screen, witness the number of films in which older men (okay, aging movie stars but some of them are starting to verge on the grotesque, e.g. Clint Eastwood, Harrison Ford, etc.) are successfully wooing young women. I think it is probably inevitable that a movie will come along with the theme of a sensitive, caring monger saving a young hooker from herself. And I'll bet he gets to screw her first. He may have to die in the end to satisfy the censors, or maybe get castrated, but it'll happen. If nothing else, an aging movie star will produce, direct and star in his own vanity vehicle just to prove he's still got it.
And if you're really impatient and tolerate subtitles, check out French cinema.