Molle range backpack made an unexpectedly awesome tail bag.

[Guest brian]

While packing up for a short trip where I was going to do some hiking I opted to use one of my range bags and intended on just wearing it, but I found that it strapped to the back of the bike perfectly using the side-cinch straaps. I'm using this bag.
 
 
Not a tail bag, but fit the part very well for what I needed. Added bonus, throw it on as a backpack and put a large watterbladder in it for riding or hiking.  Sharing this as I've been wanting a solution other than buying more luggage for a good tailbag and this has a low-30s buy-in point.