Are you referring to a lock to hold the roof up when deployed? If so I'm not sure if any manufacturer offers them. The door on my Coleman and the cranking/lift system are what holds it all up.
If it concerns you I guess you could buy a piece of 2 x 2 lumber from Home Depot or Lowes and cut it to stand up next to the roof posts. Paint it white and use a few bungee cords to make sure it stands up vertical. Heck you can even measure the length needed and have the board cut at the store for probably an extra dollar.
.
2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup