Actually, the Toploader Pro 65 AW will work perfectly as long as you reverse the hood on the 24-105mm. That case fits my gripped 7D or gripped 5DII with any of: 16-35L II, 17-55, 24-105L, TS-E 24L II, 35L, MP-E 65, 85L II, 100L Macro, 135L.
As for lens cases to sliplock to the side, unfortunately I'm not familiar with the 'new' cases. But, the old Lens Case 1W is a perfect fit for the 24-105 with hood reversed. The 16-35 II also fits if you remove the hood and place it over the barrel of the lens from the mount side. Lowepro's sizing charts often do not consider the hood. I suspect you can compare the 1W specs to the new line, if that helps.