The Charlton Heston character Harry Steele has some notable similarities to Indiana Jones, especially in having a rival archaeologist in pursuit of the same mystical artifact. The character was based loosely on a fellow named Hiram Bingham III, whose archeological world view was rather "Belzonian".
But as original source material for a two fisted, manly hunter of antiquities you still have to consider Belzoni as a candidate. Lets look at some evidence from the films and from the life of Belzoni.
Looks good in a turban:
On the unexpected detour that led Giovanni to Egypt he had along his wife and a young servant, James. A trio not unlike this one from the "Temple of Doom" incarnation of Indiana Jones.
In Raiders of the Lost Ark Indiana Jones had a nemesis. Belloq was a renegade French archaeologist aiding the enemies of his country for his own personal gain.
|Pretty much the same guy with facial hair.|
But it was on a trip to the Holy Land were we see her true nature. Returning from a particularly difficult expedition she announced that she was going to fulfill a long time desire and travel to Jerusalem. Off she went with the servant boy James, both of them dressed incognito as Mameluk youths.
At the River Jordan a guard actually tried to stop her from approaching the river before the approved time. Sarah struck at him with her whip! When he drew his sword she hopped off her mule and dared him to touch her. He dared not, as Sarah just walked past him.
The writing credits for Raiders of the Lost Ark go to George Lucas and a Phillip Kaufman. I really wonder if these gentlemen-I'm thinking Kaufman-encountered the biography of Belzoni in their research. If so, could the above incident have provided the origin of Indiana Jones' most famous prop?