Pick it up at your local Walmart for about $12. It's quite thick, it's weatherproof, and the entire inside is lined with a soft material.
You'd be hard pressed to find a 'motorcycle' cover that's this thick and weatherproof for less than $50, and it'll probably only have a soft lining by the windscreen.
Walmart has 65" ones for slightly cheaper, but they are thin, flimsy and not nearly as good as this 68" one. Make sure you grab the 68" pictured.
Here are the pics of the cover on my bike:
Here is a picture of the inside soft lining. The entire cover is lined with this, not just certain sections:
