Annerol: type Diva and/or Keeper in the search box and check out some of the threads regarding menstrual cups. It sounds like that may be the best option for you as most of them will work for 8-12 hrs. My only suggestion would be, if you opt to go that route, buy the product NOW and get used to it now before you do the ride, that way it'll be normal and natural instead of yet 1 more thing to try and deal with. I don't wear anything under my shorts, it just Sounds uncomfortable not to mention the fact that it would be another thing to rub in the wrong place!