In the US for vacation: OPK help!

Ch
Hi all, 
I'm in the US for a vacation and I want to buy some OPK test. The ClearBlue advanced is here much more expensive than back home so I don't want to buy that one. The other ClearBlue digital is confusing as you don't really see progress. Which OPK test do you use and where did you buy it? 
Thanks!!