gardengirl: If you are unsure of sewingpartsonline, you can order from Amazon. Kens Sewing Center sells through amazon which is where my new bobbin case came from. It is not 2 day shipping but is free shipping. When shopping on Amazon for the bobbin case you need, just look over to the right side of the screen under the "add to cart" button and it will show who the seller is. I try to buy from either Amazon as seller or some company I know and can verify as an actual US company to avoid those items that end up coming on a "slow boat from china". Look at the date of delivery too and that will clue you in on how long you may have to wait for the item.
I personally have never ordered from sewingpartsonline, so can not vouch for them. Have ordered from Kens sewing center through amazon and directly from their website and never had a problem.