The first instar bed bug appears very similar to the book louse with the naked eye and is impossible to positively identify without magnification. I started using a pricey 10x bosch and lomb loupe and it worked excellently. Unfortunately I lost this device so I ordered several cheaper Carson brand 10x and 7x and 5x “lumi loupe” stand magnifiers for about $9 canadian each. I found the 7x and 5x did not offer enough magnification so I use only the 10x for bed bugs.
Of the four 10x lumi loupes I ordered only three of them worked adequately – one was out of focus and I threw it away. The difficulty with these devices is that I have to put the loupe flat onto a surface to bring the bug into focus and, the fact that I often use glue boards, creates difficulty. Not insurmountable but it is annoying.
I then did some research and it appeared that the Belomo triplet 10x loupe made in Belarus was highly regarded despite the moderate price. These loupes did not have a stand so I could look at glue boards without getting my loupe sticky. I ordered two of these devices at $32 USD each and they work very nicely- just as nice as my first pricey bosch and lomb. I now carry one on my keychain. The image quality was not that different from the better functioning lumi loupes I had been using. On the other hand if you got a poorly functioning lumi loupe sent to you it would be pretty much useless. Therefore you have to order at least two lumi loupes in the hope that one of them will work adequately.
If cost is a large issue I recommend ordering two 10x Carson lumi loupes with the hope that at least one will work. If you want a nice small convenient package and a device that works well then order one Belomo 10x triplet.