You can go to the Adventure Medical Kits web site as well as other sites and purchase small amounts of whatever item you need. Most pre-supplied medical kits are way overkill, heavy, and full of stuff you'll never use. It's much more practical to build your own.
I include about 6 blister blocks, 4-6 pain pills, 4-6 Imodium, a small tube of neosporin or bacitracin, a strip of Leukotape (12") and a tiny tube of Super Glue.
I use a 1/2 qt. freezer weight baggie to carry the items and put it in my clothing stuff sack.