metal speedo drives

my nylon speedo drive is worn out after only 500miles, so I'm going to replace it with a metal one.
I was going to buy an MB one, but thought I'd check ebay first. I found metal ones for £10 as opposed to £40 for the MB ones.
I'll pay £40 if I have to as I have total confidence in MB and if it fails I know they'll honour it. BUT if £10 buys a £40 item I'll have that (obviously).
Anyone have any experience of ebay metal ones?
I was going to buy an MB one, but thought I'd check ebay first. I found metal ones for £10 as opposed to £40 for the MB ones.
I'll pay £40 if I have to as I have total confidence in MB and if it fails I know they'll honour it. BUT if £10 buys a £40 item I'll have that (obviously).
Anyone have any experience of ebay metal ones?