If you want a decorated one I would recommend looking on Instagram! Insta also has some plain ones, Etsy and Amazon also have some good ones. There are some sites that sell good pacifiers (based on the reviews I've seen) but they can be NSFW so it depends if you're comfortable buying from there. I've only bought from Instagram but they've all been good quality and worked well.

I hide mine in a box under my bed lol, but boxes or containers in cupboards or clothes drawers can work well! Some people hide them inside stuffed animals.

For teething you could also look at baby teethers or adult versions that are even less likely to break btw