I'm currently using this holder. It's a little cheap but it holds the phone firmly and I only paid $1 for it. Dollar Tree sells $1 selfie sticks with that exact mount. You just unscrew it from the stick and screw it onto your tripod!
I'm using it back and forth between a small table-top tripod that I have had for years (similar to this one) and a bigger one that I borrowed from a family member.
I'm going to pick up a tripod of my own soon (this one most likely) as well as an ND filter and maybe a fisheye lens to play with.
I got it on amazon. Link below.
http://www.amazon.com/gp/product/B00OS9E6AO?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
I actually didn't have anything to use it with, but I bought it on the off chance that I'd get a tripod.