The iRig Pre is a neat little bit of kit, but the mounting options suck. It comes with a little hook and loop strap and that's the only option. Well, I resolved to fix that problem. It works for me, so here you go.
This is a little sleeve that holds an iRig Pre and allows you to mount it on your hot shoe or wherever you would like. I printed this in TPU and the iRig Pre slides right in, but stays in place firmly. There is no hole in the bottom, but I simply drilled and tapped mine to 1/4-20. With a 1/4-20 thread, you can attach it to anything. There is a little cutout that accommodates the gain knob. I have tested this spot for weakness and with TPU it is plenty strong. Anyway, I hope this helps someone else. Cheers!