Help! All the booster seats have gone!

[Axolotl]

Wondered if anyone could suggest where I might get a booster cushion, preferably online. Everywhere is out of stock so there is obviously a mad dash before next week's law change.
What I'm looking for is, I think, known as a booster cushion, which is the one without a back. Any advice gratefully received!

Have you looked in Argos?

Woolworths have some for about £10. otherwise try Boots.com or Halfords ?

Thanks for those suggestions. Halfords all out, couldn't get Boots website to download but will try later. Hadn't thought of Argos or Woolies..thank you.
Honestly, though, it's amazing - every single one is out of stock, even on more obscure websites!

tesco have them in stock

toysrus had them all on offer last week.

Thanks so much, everyone. I've just bought one from the Boots website. Got a bit worried for a moment there - we've been using a cushion for our (tall) seven year old for ages!
Thanks again!