Where can I buy coconut with sponge like thing in it ? ( Locally it's called guanga or something ഗ്വങ്ങ)

So ever since I was a child I have eaten this delicacy from coconuts and as you can see, these got a spongy texture. Yeah we had many coconut trees where we lived. But mind you, it's not on all coconuts. But recently when I approached some coconut vendor for buying this, his response was not very positive. Tbh, I urgently needed it coz I'm thinking of including more soul food a daily basis. If you guys no any place where I can buy this regularly, it'll be of great help.