Although grim golems can get overseers like other Therian units, and Rackham produced a model of one as part of their Legends range, there are no cards for them. After rwwin asked about making some cards on the old English-language AT-43 forums, I came up with the ones shown on this page.
The cards were created by taking a storm golem overseer card and removing the model pictured on it using Adobe Photoshop to clone-stamp other areas of the background over the storm golem. A photograph of a painted grim golem overseer, supplied by rwwin on the AT-43 forum, was then pasted in. The nanoblaster shown on the original card was removed in a similar way and the repear blades entry copied. The name was copied from a normal grim golem card and moved about a bit to make it fit better, and finally the other cards were created by copying the game data from other storm golem overseer cards.
To be able to use the cards, you will probably want to save them on your computer so you can print them out for use in a game.
The exact way to save an image depends on the web browser and operating system you are using, but in general, two main methods should probably work:
(If you are using a mouse set up for left-handed use, press the right button instead of the left, and vice-versa.)