I would talk to your dentist. They can probably pull the offending tooth and replace it with a nice gold one for a few hundred buck that you can wear all day every day.
Or a veneer.
My last dentist actually made me fang caps that snapped on my eye teeth. He did it for the material and shop costs as he had never been asked to do this and was kind of into the idea.
He had been approached by folks wanting permanent fangs but wouldn't do it because of what that does to your bite, gums, jaw, etc.
I think it was around $250.
If you only want it for one day, I would go to a costume shop.
Of course, I say that here in Burbank where they are plentiful, but there must be online places to order stuff.
Cinema Secrets is a big shop near here, maybe they sell online?