There are some screw in tree steps that are small enough that one can hold 8 or 10 in the hand. Don't know if they're made anymore, but there was a place here in Wisconsin that made/makes a step they call the "Happy Hunter." Very compact, very strong and very stable. The screw was housed inside a u-shaped piece of metal which folded out to act as a lever in turning in the screw into the tree and then , when it's lower end was pressed back into the tree bark, it served as a jib (I think that's the right word) holding up the screw part. The protruding part of the housing even provided a little lip to keep one's boot from slipping off.
One of the problems my hunting partner ran into with using bolts in trees in November and December is that the bolts either froze into the trees, or when he took them out, the holes filled with water/sap and froze, so it wasn't just a matter of slipping the bolt in them when he came back.