Managed to break my tax disc holder as I frustratingly tried to get the bloody disc out (it was late, I was tired)…
Been thinking about getting a lockable one, or one of the cylindrical ones for my KTM… any recommendations? 
Sounds like you’re talking about an oxford oberon…
http://www.sportsbikeshop.co.uk/motorcycle_parts/content_prod/76900
I use one of these.
http://www.sportsbikeshop.co.uk/motorcycle_parts/content_prod/73943
They’re both waterproof and very good from what I can tell.
I have one of the hexagon ones, waterproof and functional but it’s a bit of a pain in the hole undoing all the fiddly bolts to change the tax disc. That tube thing looks more user friendly.
I realise that it only needs doing once a year but I did it last weekend and I’d put it off for a month because I couldn’t be arsed with it.
OK, I’m a lazy bugger.
I had one of the hexagonal ones and the bolts didn’t undo at all so I ended up snapping them