Do you have a budget? Do you know how much your LO weighs? And what year is your Astra?
I would strongly recommend you keep him rear facing at least for now, as it's so much safer especially for babies up to a year old (including a bit over age 1). But for the next stage seat you have a choice of:
Forward facing with harness (don't recommend this as he's still so little and vulnerable to a frontal impact).
Forward facing with impact shield (don't recommend this as more recent research hasn't been favourable towards them)
Rear facing up to 13kg (about 2) and forward facing from then on up to 18kg or 25kg.
Rear facing up to 18kg (about 3-4) and most of these can go forward facing (to 18kg) as well if you want to.
Rear facing up to 25kg (about 6-7) most are rear facing only, but one can do both.
Some seats incorporate a booster seat for when the child is older. I don't recommend these for a 9 month old, they are more suitable when a child is reaching the end of the toddler stage and only needs to harness for a short time (e.g. needing to vacate seat for younger sibling).
If your child is very big for their age, the ages are more like 1.5/2.5/4.5
If your child is small for their age, the ages are more like 2.5/5/8.
Any ideas/direction from that info? :) It's well worth doing your research on this stage of seat.