From your other posts, I'm presuming you use pin-on diapers? Maybe try pinning them up higher around your waist? My waist is smaller than my hips, so I have to pin/snap/velcro pretty high up to keep them from falling, low rise is really no good for me.
Maybe you could try plastic pants with snaps, since you can get a tighter waistband on those? I really have no experience with plastic pants, but my cloth training pants with an elastic waistband definitely slide down more than my snap-on diaper cover.
Or, alternatively, a little DIY: If you own a sewing machine (or know how to sew by hand), you could add a snap to the waistband or your plastic pants to make them tighter when you wear them. For this, you need
A strip of fabric
A snap (the strongest you can find)
Needle and thread
Turn the fabric into a kind of tab shape, attach one end to the waistband of your pastic pants (so that it lies flat against the waistband, not horizontal to it), attach one side of the snap to the other end, attach the other half of the snap to the waistband so that when you close the snap, it pulls the waistband tighter around your body.
This is not a good idea to do for overnight use since it might prevent a perfect seal around the waist, but for daytime when you're upright and no moisture will escape from the top of the plastic pant, this should help with drooping.