$20.00
Here are some places to buy inserts online. We recommend IKEA for value (they now sell online).
We recommend sizing up 5cm for squares but not for the small lumbar/rectangular.
Click on the below logos to go straight to their product listing.
30x50cm -> 12x20inch
40x60cm -> 16x24inch
45x45cm -> 18x18inch
60x60cm -> 24x24inch
70x70cm -> 28x28inch