We have scissors stairs but our truck is too high up for them. I was thinking step stool but didn't take into account the handle thing at the back. Last time out we used a couple of cinder blocks...
I recommend you take a look at the little giant (jumbo) 3or 4 step ladder. I replaced my steps with one of them several years ago. They fold easy and I hang them on a rack on my ladder. They are very stable. If you PM me I'll send you a picture. If you search the net the prices vary.