I'm making one next week for a friend so I'll do a tutorial and post; it's REALLY easy to build.
I got a handful off of Ebay a while back. I'll see if I can find the source and post. The problem with locating the meter is almost every listing is for a 2-6 cell tester. I found a lot of vendors even listed theirs as 1-6 and "testing one cell", when in fact it would only work on a 2-6 and their claim was it tested "one cell of 6". Kinda misleading so be careful who you order from.
I made one using a 2AAA box, but like the blue box better