I figured out after about half an hour that the tag word I needed to search was "minky fabric" And finally all my options were presented before me. I found that yes the online prices were not substantially better than the fabric store and sell by the yard instead of by the meter (which means the prices will appear lower since a yard is shorter than a meter).
However after some digging, I settled on this one from OnlineFabricStore.net:
|Minky Smooth: Camel Color|
The color is camel which matches the darker shade in the pattern of the fabric I have, and it was only $7.35/yd and free shipping. In about 5-7 days I can expect to pick it up from the US mailbox and will have to start this whole ordeal with the sewing again for the underside.
There were so many beautiful options and the fleur de lis or the paradise patterns would have been beautiful. Even the minky dots were tempting. But in the end, the underside isn't something that will get showcased when the cover is on the piano. So I went with plain functional mono-colored fabric.