I make nearly all my bird supply purchases from GlamGouldians.
Here is what I have been using for my finches - one of the first things I did when I got my finches was lose the ginormous seed cups (parrot size, if they weren't also plastic). You could get half a dozen Bengalese in one of those, given the clown-car-crowding nature of the birds, LOL!
My goals for a feed cup are mainly three:
1) keep the seed clean and poop-free - that means too narrow for them to turn around and poop in it.
2) Too small for attempted nesting
3) won't collect a layer of hulls that keep them from getting at seed - basically that means a fairly shallow cup so I can tell at a glance when to dump and replenish rather than having to take ginormous cups out every day and blow hulls off the top.
So these:
http://glamgouldians.com/product-biscuit-cup.php
These will flip off the cage bars when my little guys take off, but I found that wrapping an elastic hair tie around the tabs on the outside keeps them where they are supposed to be.
http://glamgouldians.com/product-cuttlebone-holder.php
The above is the ONLY cuttlebone-holder I have tried that actually works and will keep the cuttlebone clean. Usually I attach a cuttlebone to the side of the cage with a long twist-tie or similar, but those are no good for parakeets, they'd bite right through and maybe hurt themselves on the wire. I tried a couple other commercial holders before this one and they were AWFUL. One in particular was basically just a poop-magnet. This one works and keeps things clean. I have it in the finch cage also.
http://glamgouldians.com/product-art321-watertubew.php
I use the clear one for seed, to replace a similar feeder. The one it replaced was made of really soft and not at all sturdy plastic, but the shape of it was better somehow. I'm not sure exactly how - partly it was more steeply slanted so seeds slide down more easily. The above are really intended for water not seed, though technically they work for either.
Regardless, whatever it is about it that is different, my finchly duo much preferred the old feeder. With this one, they scatter more actual seed instead of just hulls. I don't know if they're just mad and having birdly temper tantrums, or if its something about the design that makes it harder for them to feed from it. It's not TERRIBLE, but as far as actual usage, the old one was better. At least they don't turn around and poop in it, nor try to lay eggs in it. They don't scatter THAT much seed, maybe 90% hulls and 10% seed ends up in the bottom of the cage.
I tried these:
http://glamgouldians.com/product-egg-cup.php
I still use these for the parakeets because they are too small for them to turn around and poop in - but not so the finches. Plus, shortly after I put one in their cage, I found my female finch trying to nest in it. At 1.5" in diameter, they are just large enough to be a problem with the finches
She has another version called a "Mineral Treat cup" that is round with a flat bottom and about 1.25" across and about the same depth that MIGHT work for the finches. A quarter inch is a lot when you're only 4" long, LOL!
I had been using Luscar Thumb cups:
But these are no longer available. I wish I had 100 of them. In fact I just found out today that Luscar (AKA Springfield Tool & Die) went out of business in 2005. So apparently those are gone forever now - and I remember using those 50+ years ago, so that's a long time they were being made.
So I've been hunting something appropriate as a replacement as they are my favorite cups for finches. Big enough they can perch on the edge and eat out of the cup, but too small for them to turn around and poop in or try to nest in. Maybe the mineral cups will do:
http://glamgouldians.com/product-2gr-art41-cup.php
For water I use the same tube silo an earlier poster mentioned, the JW Pet Insight Water silo:
This comes in a small and a large. The small is fine as-is, but the large one tends to tip back from the cage so the water doesn't flow down into the cup the way it should. I solved that by taking the metal clip from an old water silo and using it to clip the top of the silo to the cage.
So personally - given those clips aren't available for purchase by themselves - I only will buy the shorter of the two versions. Besides, my finches will empty the silo if I forget to give them their baths often enough so there's no real use to having a larger silo for them to splash all the water out when they are annoyed with me, LOL!