Oh my gosh! Radiant Lotus, I love love love these ideas!!! I am totally and completely lacking any sort of creativity. Would you be willing to send me instructions for both of these? I am totally impressed with your ingenuity :)
Sorry, I don't have any patterns to offer, but for the diapers I truly just tore a flannel sheet into squares. (I zig-zag stitched around some scrap squares to make cloth wipes, too.) There are YouTube videos a-plenty to show you how to do the origami fold. I didn't hem them because it made them bunchy and bumpy. Some of the edges frayed a bit in the wash, but usually by the time they lost much size my little guy had grown and was ready for me to rip up some new diapers for him.
The long pants are easier to make than the briefs. Find a sweater that's at least 80% wool (cashmere works too, but doesn't felt as well so needs to start out dense or you'll need two layers) and wash it in hot water, cold rinse and pop it in the dryer. Check it now and then to make sure it isn't getting too stiff. Sometimes they need a couple of rounds to get tight enough. If you have a pair of pants that is the size you want for your soakers, lay that on the sleeves to get length and crotch seam lined up. Stitch up the crotch seam with the sleeve cuffs becoming the ankle cuffs, and the sweater's waist band can be stitched on for the diaper waist band, Sometimes I add thin elastic threaded in and out of the waist to make a paper bag style waist, or put wider elastic through a folded over and stitched casing. I cut appliques from scrap wool (other fabrics will wick the moisture and end up soaked) and hand stitch them on. I've also needle felted some cute designs onto some of them. I have some more pics of some that I have made here for some more ideas: http://www.facebook.com/pages/Smiling-Hearts-Custom-Critters-and-Clothing/156271894414477