Get a " ROAD MORPH ".
As stated, it is larger and bit more expensive, but it works very well. The longer plunger also means less strokes to get the job done.
I hang mine on the underside of the down tube, behind the front wheel between the pedals. It's Silver/Alum. and Blk., just like my Roubaix.
It just looks like it was meant to be there !
............... ;>)"