Last week I picked up three stainless-steel grill knives at Academy. They're shiny and they have long round handles. They were ridiculously cheap: $2 each. They had metal loops on the ends for hanging them up; I was able to remove those with pliers.
I anticipate that they'll make great juggling knives. I've been using grill knives that I got at Goodwill for about the same price, and those had flat handles that were not as nice to juggle, and the handles were wood. The contrast between the wood handles and the metal blades emphasized the long handles...I think the all-metal knives will look much more dangerous. They're certainly shinier.
Knives made and sold for juggling cost as much as $30 each, so I'm happy to try some for a lot less. I'd insert the usual pro forma disclaimer here...don't try this at home, kids don't do anything crazy like juggling a knife...but since I do it, that would be silly. Instead, I'll note that careful, close-up inspection of any knife actually juggled tends to reveal that it is quite dull, and that I plan to show my knives to a grindstone for that purpose, until they have an edge almost a millimeter wide. That's pretty dull, and yet still not something I want landing on an arm, a toe, or a face. Especially not mine. Also, it's really stupid to play around with a juggling knife over a laminate floor. Don't ask me how I know that.