Booster seat with head support needed for 8 year old

[roundabout1]

Sorry if this is in the wrong place. Our dd who is 8 has CFS/ME, she is very tall for her age and so doesn't need a booster seat any more but still uses her Britax Evolva as she likes having the head support when she sleeps which she does even on a very short journey. Dd2 is ready to move up from her front facing baby seat (stage 2?) we were going to put her in dd1's Evolva but have realised that dd1 will struggle without a head rest. Are there any larger hi backed boosters that have more room around the head. Or are there any alternatives for dd1 to us. All I could think of was one of those cushionedneck pillows but have tried them and dd1 hates them. Tia x

Have you looked at cybex pallas?
It's supposed to be suitable to age 12 and my toddler loves it. She finds it very comfortable to sleep in.

The diono Monterey is really suitable for older children from what I've heard. We have a jane montecarlo which is also adjustable by width and height.

We have the Jane montecarlo car seat which is also meant to be good for children up to 12. My DS(4) sleeps in it, it has lots of adjustment to support the side and head and seems to extend quite high. There is also a small amount of adjustment to the recline position. We really like it and will be buying a second one for DS2.