I have found this maker in US: www.bearingbuddies.com
There is one in UK: www.trailertek.co.uk/ acatalog/BB101.jpg
Looks a little bit different, but works just the same.
I have copied the photos from the webpages. Well aware that i'm not allowed to do that. I let the photos be here till someone tells me to remove them! I think theese bearingsavers are good things. Making it more safe to drive around in bad conditions with our boattrailers, especially now, wintertime. I have seen what happens when bearings get jammed due to bad grease or none at all. The friction will make the brakepads and the drum even hotter. This will be to much for the bearing. Finally, It's not a pretty sight when a wheel leaves the rest of the trailer. No horrorstorryies to be told here! It's a lot more fun to be home in time, safe and sound.
There are a lot of places to order on the net. If you order them, measure the diameter on your hubs, so you get the right ones. Safe ride and Tight lines.