Same thing happened to mine. Could barely get a few of them off. Shop wanted to charge me $5 a piece to replace all of them. I found this whole set on amazon for $20. They're solid steel, no cheap cap. They look and fit perfectly.
Just search DPAccessories D3116-HT-2305/20 on amazon and you should find it. I think I paid about $20 for the entire set and free shipping!