If your headphone has a long straight plug, then I suggest that it not be plugged directly into the player, but instead in a Y cable or cable with a volume control that has a right angle plug, with the right angle plug being plugged into the player. Having a long straight plug sticking out of the player may put plenty of force on the player’s headphone jack if it is pressed against.
An L shaped adapter doesn’t have the same effect as a cable though, since with the L shaped adapter if you press against the long straight headphone plug it could still damage the player’s jack. Having a right angle plug, then a cable, then a jack for the straight plug gets the long straight headphone plug out of the way so it doesn’t damage the player’s jack.
I am suggesting the use of something like this if your headphone has a long straight plug.
What you are describing is Replug. It is a bit expensive though($11) and received mediocre reviews. The Y cable is typically $3 or less, and has the advantage of providing a second function, which is allowing a second pair of headphones to be connected.
Others like to use a volume control cable with a right angle plug, such as this.