Know what you mean. Any decent china shop will let you try out a teapot first, using water. What to look for is one with a sharp edge on the spout. (Silver and aluminium pots were always the best pourers in this respect. Even Le Creuzet haven't got theirs right. Good luck!)
Agree that any decent shop will let you try out a teapot before you buy....I've insisted myself before now!
You want a red one....try the Yorkshire Tea website....they sell teapots which are red and also mugs with their red logo on. You can get them with the tokens from the boxes of tea, or pay for them normally. The one that I have seems to pour to mine and OH's satisfaction!