EXP Pedal with switch

You can use any expressionpedal to engage the Wah effect if you select bypass@stop as the pedal mode. No extra button is needed.
As soon as you move the pedal the wah will be activated.

But I think he wants to be able to switch between volume and wha pedal. You would need an expression pedal with a switch for that or you could assign any other switch for turning wha on/off. However I do not know whether any of the cheaper pedals offers a toe switch.

Yep, I disengage the wah from the pedalboard if I need, and use a non-switching Dunlop pedal.

I have my expression pedal type setup as a wah pedal, then I choose wah to volume pedal in the system menu. I set the wah to bypass at stop. To switch between a volume and wah, I just choose a different slot with an active wah effect. I used to do just what the OP was describing when I controlled my Profiler with my HD500 (prior to having the remote). It seems like a different concept, but it works great once you get used to it. Especially the bypass at stop.

I use the cocked WAH sound sometimes so I just set my Wah to stop at heel. And set the WAH to Volume in Kemper. So If I turn off the Wah on any slot It goes to volume

I have heard from this pedal.
http://www.thomann.de/gb/mission_engineering_ep1_kp_gn.htm

It has an additional switch.
I do not know if its possible to switch from Wah- to Volume function.
Maybe in Vers 4.0, which should have better access to parameters of the KPA.

Quote from Sharry

I have heard from this pedal.
http://www.thomann.de/gb/mission_engineering_ep1_kp_gn.htm

It has an additional switch.
I do not know if its possible to switch from Wah- to Volume function.
Maybe in Vers 4.0, which should have better access to parameters of the KPA.

It is, but I think that he was asking for one of the cheaper pedals.

I could be wrong but I think you'd have to find one second hand. Another option might be to build it yourself (attach a switch to an existing pedal)?