Here's a list of some pieces of equipment that are helpful in practicing and some ideas about where to find them.

Music Stand This is one of the essentials. They come in all kinds of different configurations. If you have to take it with you, get one of the folding varieties. A black stand is nice for practice at home. There are also some very beautiful handmade solid wood stands.

Metronome I use mine every day! You set the tempo and it gives you a steady beat so that you learn to play without speeding up or slowing down. They come in two basic varieties. Digital metronomes usually have a digital display. They tend to sound more like a "beep." They can be very small, and they usually have buttons to change the tempo, which means that you can change the tempo by one beat per minute. Quartz metronomes usually have a dial and they make more of a "click" or "tap" sound. Some of the newer metronomes have special features, such as a different sound on the first beat of a measure or a "tap" feature where you can tap your tempo and it gives you a number.

Tuner These also come in two varieties and at some point become essential. For flute, you need a chromatic one (one you can play any pitch into.) Digital versions may have an all-digital display, or may have a regular display with two dots to indicate pitch. Regular tuners have a needle. All of them have a calibration feature where you can change the pitch standard. Some models also will output a pitch for you.

Flute Peg These can be a lifesaver if you're juggling multiple instruments, but you always have to be careful that they don't get tipped over. Head for one with a solid base: it's worth the extra space and weight to keep the flute safer. There are varieties made of clear acrylic and also some beautiful ones made of wood.

Cleaning Cloths You need to have two: one for the inside of your flute and one for the outside. You can use something as simple as a rag from an old cotton t-shirt for this, and this does have the advantage that you can bleach it when it gets really dirty. But cotton can get lint on it, which can cause flute problems. My personal preferences are silk for the inside and microfiber for the outside.

Where To Get It
Flute World This is one of the best sources of all things flute-related. They have a massive stock (including everything listed above) and are usually pretty fast. They have secure online shopping, but not every item is listed on the webpage.

Carolyn Nussbaum Music Company Another all-flute shop! They also carry most of the above items and some cute flute-related gifts.