Because you are talking about using with a UC; I am assuming you are looking for glass (plastic absorbs, and dampens, the UC).
Glass Bottle Outlet is always my starting place for all things bottles. They are quality products, dependable, and don't demand large orders. You can also order as cap/bottle combos, or caps, and bottles separately; which is kind of nice for mix and matching. I am a hardcore price shopper (can you say "penny pincher?"), and when I was shopping for bottles to break down my nic for freezer storage, GBO was the cheapest (product + shipping) when I compared 5 different US vendors.
A note on dropper tops (and this is
my opinion ONLY); the soft rubber used to make the squeeze bulb, of the dropper, is VERY air(oxygen)-permeable. Not a big deal for short-term applications (1-2 months, or less?)(and depending on flavors used), but
may contribute to flavor loss, and/or nic oxidation over longer periods. If you are planning on various mixes lasting for extend periods of time, you may want to order bottle/dropper cap combos,
AND additional poly-cone caps of the same size, so you can seal the bottles for long-term storage. Just a thought...