Found a new keyword for my Amazon niche

Hi fellow warriors,

Got a question here because I found a pretty cool new keyword for a niche that I'm already doing well in.

I have an Amazon review site that ranks on page 1 for its main keyword, and already generates a decent amount of sales.

Now I found a second keyword that has great potential to rank as well, and I'm wondering what would be the best option to take advantage of this.

Let's say my existing site targets the keyword "flash drive", which has 9900 exact searches per month. So I just stumbled upon the fact that "memory stick" also gets 4400 monthly searches, and has significantly less competition than "flash drive".

What would you do to milk "memory stick"?

Of course I could just put a sub page on my existing review site to target the new keyword, which might work for the search engines, but I don't feel good about this because it would look really dodgy for any human visitors. After all, the two keywords are exact synonyms.

My idea so far is to register a second domain, i.e. "memorystickreviews.com". However I don't want to build a whole new review site with similar content to the one I already have (I write all the content myself and this would be really dull).

Maybe a somewhat thinner site that links back to the first site? Or do you have any other ideas that might work here? Maybe some of you have already been in this situation - looking forward to your advice!