Midland Rly Centre, the tools part of the former Metalsmith business are producing a set of 12" rolling bars. I contacted them today & the rollers should be available in a couple of weeks, although numbers will be limited, so if you would like a set you need to get your name of the list.
From the description the bars will be similar to the previous rollers produced, but 12" long rather than 6"
They accept card payment
Regards
Dave