Just use a larger Zip Lock bag inside and use the tank bag you like. I use that Wolfman Enduro bag on my SE for exactly what you said, wallet, camera, sunglasses, keys and a tire pressure gauge. It has seen hard rain, but not for extended periods of time. No issue.
2011 BMW K1300S
2007 KTM 525 EXC
2010 Husky TE310
2006 Husky SM610
2011 Beta 300 2T Lim Ed+ 74 RL250 Suzi