Trader Joe's has sold a frozen squash ravioli for several years (we do not have a TJs in our town, so I can't tell you if they still stock it). Our local Wegmans (a supermarket chain in the NE) has had them on and off in their store-made pasta section.
You can order butternet squash ravioli from Alfonso Gourmet Pastahttp://www.alfonsogourmetpasta.com/Ravioli/ravioli.html
and pumpkin ravioli from the same placehttp://www.alfonsogourmetpasta.com/r.../raviolo2.html
I have not tried their products, so this is not a personal endorsement.
Another source is Del Monaco Specialty Foods , but I do not know if they sell to individuals (they are a supplier to restaurants). Try their site athttp://delmonacofoods.com/
And of course there are many recipes on the internet if you'd like to make your own. A nice topping is a simple sage butter.