This. In the States my local Ace Hardware has these 0-rings, along with 20-30 other sizes. Some places don't have hardware stores, I guess, so you may have to order them online.
The O-ring works, not all that good, though. Pads stay on better, still a little bit floppy and can come off. Sound and comfort level makes up for any inconvenience.
It does lose a little bit of bass, so for me the stock pads sound best, since they're the most bass-heavy of the pads.
Are the O-rings from Ace Hardware 3/16"? I tried those and they are a smaller diameter.....the 3/16" from the web site I linked are 3/16", and I have never had a problem with them coming off!