The best bet would to be finding only the spices without the tea because of the astringency that tea can add. That said, I'm brewing a dunkelweizen with chai right now and I couldn't find the chai spices anywhere reasonable. I found a store that sold quality loose leaf tea that I have used. I wouldn't use cheap bag tea to add to beer because it's usually crappy quality and really astringent. I brewed 1oz of loose tea according to the temp and time recommended for tea by the store in a French press (about 12oz water) and added that at flameout for 5 gallons. I plan on adding more made the same way to taste when I keg it in a few weeks.
Fermenters: Lambic, Pumpkin Pie
Kegged: Skeeter Pee, Barn Burning (Smoked Saison)