I have a bike, 76 cb550 F, that also has the I-dare-you-to-find-neutral-when-hot problem. This is caused by a dragging clutch putting a preload on the trans components. It gets worse with aged oil. Switching to Honda's semi-synthetic helped some. It tried re-adjusting, also helped, but did not eliminate the condition. The clutch slips a little, too, under high load, high power conditions. I bought a new Honda clutch to put in it... waiting in the box. In the mean time, I developed techniques for coping with the problem.
1) It's only an issue when the bike is completely stationary. Make all your gear selections while the bike is still moving. Almost any bike motion allows gear selection. If you know you're going to want be in neutral while stopped, put it in neutral before you've stopped or just as you stop.
2) If you have stopped, rock the bike fore and aft while applying a bit of pressure to the shift lever. Too much and you'll skip into the next gear. But, you know how much pressure is needed to shift while driving, so use just that amount to get neutral and move the bike to get the rear wheel, chain, and trans gears to turn enough to allow the forks to move the sliders in the trans... snick
Cheers,