Portable beds???

[Chickpeas]

Hi
bit of a strange one this but because my son can't sit in a cinema chair we always end up with him lying on the floor amid the popcorn, spilt drinks and unmentionable crap that seems to be on cinema floors. It is unpleasant and dirty.Usually this is in the disabled bay reserved for wheelchairs if it is unoccupied and we sit on the seats alongside. Does anyone have any ideas on what we can take for him to lie on that is thicker than a blanket but not enormously bulky, like a futon matress?
We do get some funny comments or snidey looks when he lies on the floor but I would rather he was comfortable then shouting, spinning, etc

Any ideas?

how about something like a camping roll mat or similar? they are made of a high density foam, and so are reasonably comfortable, and usually roll up easily enoough to fix to ruck sacks etc, so are fairly portable?

a short length thermarest type camping mat? They roll up small, self inflate to about 3 or 4cm . some go thicker but they don;t roll quite so small.
www.winwood-outdoor.co.uk/acatalog/Self_Inflating_Mattresses.html

We found a yoga mat that is like a bed roll but a bit wider. It has straps and a carry handle. Its a bit bulky but at least I won't have people shouting 'Sshhh' and tutting when he fidgets. Thanks for the suggestions.