You were in the right place T10 is basically the generic name for the socket the 921 bulb uses. So any T10 based bulb should work instead of the 921, provided of course, that the physical dimensions don't exceed the capacity of the bulb opening/holder.
My Edge's 921 socket is OEM i think, and it holds on to the OEM bulb pretty tightly. I have tried multiple LED products in that socket, and as to whether the bulb you buy is a little loose in the socket, that will vary. The current ones fit pretty well.