If you want a single lever ball head I would suggest you have a look at the Triopo RS range. There are 3 models the RS1,2 and 3 - I have the RS3. It is small, light, cheap, very smooth operating and easily holds any lens Canon currently make. Almost certainly overkill for what you want but it is seriously cheap and seriously light. If you live in the US they are sold under a different brand (I don't know what it is - sorry) but are available on E Bay.
I have not tried the smaller models (RS1 and RS2) but I would expect the smallest to be happy with unbalanced loads of 4 Kilos or so. You will need to budget for a QR clamp, I would suggest that it is Arca compatible (Triopo's own one is pretty good).
Attached are poor quality images of my RS3 - yes that is a Canon 600 F4 L IS + 1D Mk4 on top, yes it will easily support it at any available angle and yes it does show up the flex in a Gitzo systematic tripod!