There's a few solutions here. If we rule out any chance of deleting these pages (would deleting them effect your ability to create products from those manufacturers in the future? Not sure what system you're going with here), you can take steps to limit any adverse effect this could have.
First, you could add the following code to the head tag of your HTML:
This can be easy to implement, but robots and crawlers have been known to ignore this directive.
Alternatively, you can add text to your Robots.txt file, telling crawlers to ignore certain pages. In this case, you might want to add:
User-Agent: * Allow: /
Disallow: */littermaid-manufacturer
You'd want to do this for all of those empty pages, but this could take time and can get quite messy if there's dozens of these pages you want to block.
I'd highly recommend implementing a rel=canonical system onto your site (I would even if you didn't have this problem). This schema language can help to reduce any negative duplicate content effect. SEOMoz provides a detailed canonical guide here, which I recommend reading through.
Finally, as you've mentioned, adding content to these pages would also be a good idea, regardless if they're in use. If you had a detailed description, say roughly 300+ words (very broad figure, go as detailed as you can), it would dilute any duplicate content elements on the pages. In addition, it will be useful to have on your page if and when products are eventually added to them, which can be very useful if you wish to optimise the page itself. Put it in the first paragraph under your topnav for now and you can always move it later.
Hope this helps - to summarise, I'd recommend implementing rel=canonical on your site, adding content to those pages and, if you want them blocked from crawlers completely, add the pages to your robots.txt.