Sure!
First, make the bag with "rolled" edges at the front. In other words, fold the two layers of cloth comprising the lip of the front of the bag in about 3/8 inch or so and sew it to add stiffness to the lip. Soak the bag in walnut die or whatever you like to get the color you want, then let it dry.
Now, melt your beeswax. 100% is OK, but you can cut it with beef or deer tallow if you want. I don't find the proportions to be critical. I have used 50-50 and it seemed to work fine.
Lay your pouch on a grocery bag or even brown wrapping paper. Paint the mixture on. It will harden practically as soon as you paint it on, but don't worry. Really glop in on. Now, take your wife's best iron (or go buy a cheap one, your choice.). Take another sheet of paper, lay it over the pouch, and touch the hot iron to it. It will melt the wax right into the fabric, and excess will be blotted onto the paper, making true waxed paper for use in wrapping your salt pork or making paper cartridges. Repeat the process, hitting the seams of the bag which you probably missed on the first application.
Once you are happy with the results, that the wax has fully penetrated and there are no spots of exterior wax buildup, you are done. Let it cool. The final product will be stiffer that a light leather bag, impervious to water, and authentic as all get-out. It will not be brittle, as the wax has penetrated the fibers of the material and is not just a surface coating. As mentioned, I will generally use a leather flap, sewn to the back of the pouch near the top and this adds additional stiffness to the spine of the bag.
It will hold it shape just fine. It is not like a haversack which is typically made of one layer and does not hold it shape at all when loaded. It is not tacky, and does not get stiff in cold weather or slimy and sticky in hot weather. I used mine in zero weather and in summer trail shoot weather. I have mine full of the usual shooting pouch implements. It works fine.
Hope this helps.