What kind of bay adapter do I need to buy for a SSD?

The adapter may be included with the SSD to put it in a 3.25" bay.

This or this should work fine. Standard desktop drives and drive bays use a 3.5" form factor, so what you're looking for is a "2.5 inch to 3.5 inch mounting bracket".

^5 +1 what clarkjd and sminlal said. Some of the "retail" versions come with a bay adapter, SATA cable, and maybe a cd-rom disc with a few goodies. You have to check the specifications to make sure.

My ssd did not come with anything so I bought the Silverstone bay adapter:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Works for me. It came with a plastic bag containing lots of screws in two different sizes.

TIP - Attaching a solid state drive to a drive bay or a bay adapter is a lot easier if you use a magnetic screwdriver.

Weird -- my HAF 912 case came with an SSD bay, but your HAF 922 doesn't. Just buy the cheaper of the two brackets sminlal linked.