Actually, Sylvania discontinued the amber bulbs that are coated some time ago.
The Silverstar corner/signal bulbs that are in auto parts stores now are just regular white bulbs with a coating, hence they no longer have an "A" after the bulb number.
There are still places that are selling them online, but at inflated prices.
Alternatively, there are now SILVER coated amber bulbs...but not through Sylvania. You can find them on ebay, just cheapo generic made in China/Taiwan stuff, but they seem to be ok for the price, just not as bright as regular brand name bulbs, probably due to the low quality bulb used as well as the coating.