Hi, I bought both items from Brick Lane Bikes earlier this year and I didn't get around to using them on a single chain ring configuration.
The Chain Keeper is the 35.0 diameter version and it can also be used on a smaller diameter seat tube.
Chain Keeper details here: https://www.bricklanebikesshop.co.uk/products/paul-components-chain-keeper
Extension bar details here: http://www.paulcomp.com/chainkeeperextension.html
Pictured available on request.
Total cost to me was £73 inc postage, looking for £50 inc postage.
Thanks for looking.