The Gemara (שבת, פ׳ במה בהמה) has lengthy discussions about animals going out with covers tied to their udders or other extremities, and repeatedly (briefly) mentions a Zav wearing a sac to catch his discharge. What about a Zavah or a Niddah with a "Moch"? Is there any Issur of carrying, or a rabbinic prohibition lest she later come to carry it? It seems to me that this is a different sort of device (not tied on), but serving the same purpose as the Zav's, and because it's not tied it could come loose, which is the concern mentioned for the other cases. But (as far as I see so far) it isn't mentioned.