I have Telefix clip ons. They do them by request in 41,7mm, too (taking the 41mm and machine them to 41,7). They have multi-adjustable ones which are quite good if you torque them right. They are also available in black, which comes closer to the original look. Also, if you drop the bike and they bend, you can get all single parts separately, which is a nice service.
http://www.telefix-products.de/product.php?id_product=169
you can even mount them below the top yoke, as they raise the handles 30mm.
If you don't want that, take the "Racer", they do not lift the handles and are a bit less adjustable, which makes them easier to install:
http://www.telefix-products.de/product.php?id_product=215
both, as said, are available in black, too.