Just because Marinha Dourada has mattress toppers it does not make it any more likely that they will be available in Goa.
It is almost certain that they will have been sourced from Bombay.
We have learned from living here that there is a "get it from Bombay" attitude on the basis that stuff will be unavailable in Goa, or MUCH more expensive. This is rip-off city for the locals too its comforting to note!
On a recent shopping trip to the big city we were amazed at what we could get, and how cheap compared with here. Imported from Brazil Nescafe from Crawford Market was HALF the cheapest price here! If you travelled at the prices locals pay for bus or train, that one jar of coffee's saving would pay your fare (about RS200).
It was also noticeable there that the "pre-bartering price" was more like 10-20% above proper price whereas here it is 100-200%!
If I get the chance during my wanderings in the next few days I will pop i to the MD and ask.