Y'know, another fine one-shot RPG would just be a sequel to "Enter the Dragon". A year after he takes out Mr. Han, British Intelligence calls Bruce again with a mission, and this time he brings along some quasi-allies from the first film --- John Saxon and Jim Freaking Kelly.
Now, Kelly's character appeared rather dead in the last one, but it's not like Saxon took his pulse or anything. In lieu of a remarkable recovery, you could always introduce an equally streetwise jive talking sibling.
As for additional cast members / PCs . . . Bruce was good buddies with Chuck Norris, so I'd make Chuck a team member. Bruce was pretty tight with James Coburn, Steve McQueen, and Kareem Abdul Jabar, so any of them could appear. David Carridine could play a bad guy.
If you wanna get silly, you could throw in Rocky Balboa. Set the movie in late 1976, sometime between Rocky I and Rocky II.