I find I can shoot that lens handheld fairly easily, but having a support like a monopod will help, specially if you are shooting sports just so you don't get tired.
I have a cheap monopod (targus?) but I upgraded the head to a Manfrotto 234 which really makes it usable.
234 Manfrotto 234 Swivel Tilt Monopod Head - Supports 5.6 lb (#3232)
A K-5 body with this leans is easily handled by this combo.
Personally I would not have confidence in the Manfrotto self standing monopods, more so with that lens combo as I think it could easily tip, I'd rather break out a full tripod if I want to place the camera on a support I'm not holding onto.
The Manfrotto 680b is a decent unit and will hold the weight fine, adding the 234 head will bring the total to around 80 bucks, a little more if you want the quick release version.