The actor, who died Sunday at 84, voiced a character named Ready Espanosa in the small-budget animated flick, The Waterman Movie, but the film's director says they can't afford to finish it.
The director, Bryan Waterman, tells TMZ.com that Nielsen finished his voicework over a year ago but a "great deal" of production on the animation remains.
He's seeking donations in exchange for a "special thanks" at the end of the movie to help get it into theaters.
Waterman also plans to add a dedication to the movie's end.
Wrote Waterman on his website Sunday after hearing of Nielsen's death: "There is no word greater than 'impossible' to describe the anomaly I was fortunate enough to be a part of. If only for a little while, I was friends with a super hero. From a fan, to a legend, you will be deeply missed."
– The Hollywood Reporter