Sadly, no... The far side tapers down quickly to a much smaller O-Ring that surrounds the clear plastic "light indicator" window. I have found the manual online, which says that the O-Rings (mm) are 16/22 and 16/28, but doesn't specify what the dimensions pertain to. Looking at the housing, there's no way that the missing O-Ring is anything more than a standard-thickness ring, unless it's more like a rubber band shape than a regular ring.
I also found a package of replacement rings online, that are sold out, which makes them all look like a standard round O-Ring. Of course, the package doesn't mention sizes... :mad2: