First thing's first about throwing shoes, they're not your average days' shoes, the soles are special.
The sole for discus, shot put and hammer, is flat and smooth to glide more smoothly, gaining more momentum and speed to throw. You could say " Might as well just wear worn out sole shoes to throw" Well, not exactly, the sole are flat, meaning that no extra "height" would be added to your heels or your feet.
Compare this to the throw shoes
Normal Sport Shoes Throw Shoes
See the difference? The height of the sole makes a difference in throwing. When you glide, the heel would catch you and slow down your glide, decreasing the distance of your throw. AND, when you glide, you would use the ball of your foot to spin/glide to transport you to releasing your implement. So , when you use support yourself with the ball of the foot when gliding, if you're wearing sport shoes, chances is that the heel would drop down (as the heel part of the sole is thicker) and slow you down significantly. The sole of the sport shoes is also designed for non-slip so there would be more friction, interfering with the speed of the glide, while throw shoes soles are designed to have less friction between the thrower and the ground so the initial speed would not be interfered. Javelin shoes have spikes to grip on the track while running. (Sorry, don't know much abt Javelin shoes)
I have recommended a few websites and a description of the websites.
1. www.eastbay.com
I had personally ordered my shoe from this website. It has a wide range of throw shoes for you to choose from and its up to date and season. But it would frequently have sales and end-of-season sales :) It is pretty reliable AND it ships to a variety of countries (including SG) Eastbay also has products for other event categories and sports' apparel and equipment. The shipping costs about $30 (?) and its REALLY worth it. I think their shipping is by air, my pair arrived in just 3 weeks after ordering. Its brand new, not second hand. It sells a lot of brand variety as well.( Buying at end of year is much cheaper but less sizes to choose from)
2. sea.taobao.com
I did not buy from this website, but one of my seniors bought from there and it looks quite good. It's in Chinese and the throwing shoes are not branded but a China brand. They look quite nice but I don't know if they're long lasting. Some reviews said they came in the wrong size so its buy at your own risk but the shoes are only about $30 ++
100m
steeplechase
high jump
Shot Put
Discus
Hammer Throw