Not sure what shape they are, but I bought some at Lowes. They had several different sizes. If they didn't have 8" you could by 12" and cut them down. If you need something fancier you can look at www.tablelegs.com they have all shapes and sizes.

Woodturners Incorporated make excellent quality furniture legs in a variety of styles, sizes and woods.

Here is a link that might be useful: Woodturners Incorporated

Neither one of these companies has 8" sofa legs. If you know of a vendor, please advise.

You might try tablelegs.com. We bought our island legs from them and are very pleased. The Coronet bun foot series has an 8" foot. I'll link you to their furniture feet page.

Here is a link that might be useful: furniture feet

http://chervan.com/component_pgs/legs/legleadpage.html

Unfortunately, they are B2B only, so you will have to go through an upholsterer or design center to buy them.

Here is a link that might be useful: Frank Chervan

And I would be very careful with is as you are reaching what might start to become a problem for racking. For example, don't push this sofa around, lift and carry.