Prior to de-cotting, her majesty used to sleep away in a Phil & Ted’s travel cot, which is extremely sturdy, and really quite large, whilst still lightweight. She a)liked it, b)didn’t turn it over, and c)couldn’t climb out, which is an advantage over some other things we tried.
Now she is in a toddler bed, we have a ready bed (sort of inflatable thing, pretty cheap). She isn’t locked in it, but she does mainly stay in it, and as long as the room isn’t freezing, it doesn’t matter if she goes and sleeps on the floor somewhere until we find her.
At some point pretty soon, you’re going to have to deal with your kid pottering around at will anyway and drop the side right down, you get to the point where they can climb out of the cot (can’t remember when that was for us, but I think before 2), and it is safer to take the side off than have them dropping down the full height of the cot every time they wake up at night.