Look at this one. It's one of the most economical of draw forts, only requiring four warriors besides the King. The disadvantage is that it also requires access to four edge squares instead of the three that you need for the cloister. Could be a problem if you're short of space.
This "bunker" draw fort is not royal, as the king can be anywhere in the position, either inside the fort, or acting as part of the wall. I have shown him inside, and (as usual) surrounded by enemies!