RE: no harness
Matt, when I climb I use tree surgeon gear, so dont know what they sell for hunters. However, yes I DO use a safety line when climbing with a climbing stand. I take a short piece of rope (even 6mm nylon line works for this purpose), and make a loop by tying the ends together. A good knot is important, I use a grapevine or a fisherman's knot (used to tie 2 lengths of fishing line together). Then run the loop around the tree and put one end through the other. This forms a choker around the tree. Clip the end of the loop to your safety harness. If you fall, the choker will tighten up on the tree and hold you. This system requires sliding the line up the tree as you go.
You can also use something like a flipline like tree climbers use with leg spikes that just goes around the tree and each end clips to your belt/harness. This should work fine for a climbing stand since you would not slide down past your stand if you fell.