For the surreptitious or 'don't want to fill the Portapotti too quickly' wee, I've used a tupperware cornflake container for years. They wedge securely in available spaces, can be sneakily emptied through the spout and seal securely if you have to postpone emptying. Couple of drops of disinfectant in there and no niffiness either. I replace them occasionally, the last one was from Wilco and cost a princely £3. If you're surrounded by people and need to be furtive :ninja:, they also lend themselves to a fairly silent pee too, once you've got the angle right. Oops, too much information, sorry...blush blush