It comes from an old secondary source with no source notes, which is why I wanted to find the original quote. The book is David Howarth, WATERLOO: THE DAY OF BATTLE (London, 1968), p 176.
The context is Napoleon leading on the Guard at Waterloo and he has just turned aside to let them march up that ridge to disaster.
"Two of his attendant generals were begging him not to expose himself to any greater risk -- the safety of France, they said, depended entirely on him. But Prince Jerome was heard to ask another general: "Can it be possible he will not seek death here? He will never find a more glorious grave." Jerome, it was clear, did not believe that France could still be saved. But he might have known that his brother would never admit he was beaten."
I would like to find the source of Jerome's quote but, reading it over again, I see that it might be from the memoir of another officer present at the battle.