all bike seats are suitable for a 6 month old, some recline, so they are suitable for younger babies.  I have one, the only one I could get being that I also wanted to have my older son on a tag a long on the same bike, it is quite upright, and so when the little guy falls asleep, it is uncomfortable, so especially with a young child, one that is likely to fall asleep, it is better to get one that reclines, but expect to pay about double. 

Jodi

K-mart and places like that should have them. I bought mine from Midland bike place 5-6 years ago (over the road from super cheap and near hungry jacks)

but they have these better ones that you can get. they are a few hundred but can turn into a pram.

my seat cost us $100 and thats the gray ones that sit on the back behind the seat. hubby and son didnt like it at all.