We have had a similar issue with an other little cushion. I asked my Lagoon
dealer. He wants more than 400,- Euro (+ 100,- VAT) for one cushion.
So I asked the original manufacturer of the cushions
(there is a label). They want 170,- all in.
They are very friendly - but a little awkward. We needed at least 6 emails for the order - although my wife is a native french speaker.
Accueil - Ruchaud
The original fabric
is Sunbrella, basically you can have it sewn everywhere, in many cases for less money