Over the past few years I bought a variety of 1/2" drip irrigation fittings, and didn't try these until this year, and they are GREAT! The only problem is, I can't figure out where I got them and can't find them online after a world of googling. (They have no writing on them, just a tiny logo which I also tried searching for, in vain.)

Please tell me you know where I can get more of these — thanks!

Do you remember if you ordered them online or bought locally? Online I found one that seems to match from The Drip Store, maybe that's a place to start to look. DIG also shows images similar, but now it seems they've changed the design a bit.

Try Googling "Universal Nut Locking Coupling" and see if any companies ring a bell.

Btw, I've got in the habit of keeping a text file on my PC with everything I order under each store. I order a lot online and it's easy to forget about something until 4 months later you realize you never got it and then try and prove it after that time. I list the item, price, dated ordered and received. And it also lets me search for an item and see where I bought it from, and makes it much easier when I need to order the identical thing again.