This may sound super cheap but it worked for me for many years hunting with my sidelock:
After you get your load/gun figured out so you know what your charge will be, you can make up "speed loaders" using empty, fired shotgun hulls for the container.
Leave the spent primer in. For 58 caliber I used 12-gauge hulls, 20 gauge works for everything else down to 45 caliber.
Drop your measured charge into the hull, then take your greased bullet(I like minies) and wrap it in a large enough cloth patch, like a 12 gauge shotgun cleaning patch, to both contain the lube to keep it from contaminating your powder, and "shim" the lubed bullet or patched ball so it fits tightly into the hull. Push it in just far enough that it stays inside the hull but is not down onto the powder. This will leave enough of the cloth sticking out for a grip so it can be quickly removed in the feild.
When you need a reload, just hold the rifle with one hand as usual and grab one of the speed loaders out of your pocket or possibles bag and hold onto the patch with your teeth, pull the bullet out of the hull, dump the powder down the bore, then remove the patched bullet from the "hankie" and get it down where it belongs.
I know it sounds funky but it works. I have a few of these in a plastic ziplock sandwich bag that are several years old and the powder is still dry.