Lock entity onto player (no tp command)

I have noticed that someone has been able to lock a display entity model onto the player so it never leaves the middle of the screen. The way I have been doing it is by using the tp command to teleport the display entity onto the player, which works great usually, but it lags behind due to how ticks work in minecraft. 
Things I have considered and it hasnt worked:

tp command
ride the display entity on the player (cant put entities on the player)
make player ride something and the display entity ride the same thing (you cannot see the entity health bar)