This is Iris Sagan (Tesa, A-set, etc.)'s headband from Ai: The Somnium Files ripped from the game. You can print it, but it might be a bit small without tweaking. I'm a beginner myself, so I can't give you any tips printing it :( but it is totally wearable with scaling, and I printed one with petg and it held up fine at an anime convention!