Where to buy replacement foam pads for seats, not £££?

[Miljah]

Looking to replace 2 back rest seat pads for outdoor furniture, but the cheapest I can find on ebay, 16" x 24" x 4" IS £17!! For a medium density foam pad!

Any other ideas?

Try craft shops , or habadasharis there is one of each in Manchester city centre. Not sure of the £s tho