There are not any on this site, as far as I know...
Except for the Red Box that runs on 12v. But if you build this one make sure that you read the instructions properly:
http://tagboardeffects.blogspot.no/2016/10/hughes-kettner-red-box-classic-di.htmlNormally D.I.Boxes are run on 48v Phantom Power fed from the mixer, and a good D.I comes with a high quality transformer inside, so the cost of building one yourself is often higher than just buying one in the shop (which I highly recommend! Check out the ones from Radial, those are the best!)
Parasite Studio has a quite simple transformer-less D.I.Box build that runs on phantom power from the mixer, and can be found here:
http://www.parasitstudio.se/stripboard-layouts/active-direct-injection-box-diThen there is this one from TH-Custom, that uses 9v and a charge pump to raise the voltage:
http://diy.thcustom.com/shop/balanced-line-driver-v1-0/Have you seen this wonderful unit built for bass players?
I'm going to get one of these soon:
http://diy.thcustom.com/shop/all-in-one-v1-3-pcb/Hope this helps pointing you in the right direction...