vvt means volume-volume-tone ...
It's no problem to add a series/parallel mini-switch (on the last position of the panel?). A "Gibson LP toggle" would be too big and also has the wrong contacts. A DPDT On/On is needed.
Here is the page to my 400 pages wiring compendium (in German - but easy to understand!): http://161589.homepagemodules.de/t29...-E-Baesse.html
Scroll down, open the "Bassschaltung389.pdf" and save in your HD.
Drawing 2.1.01 (currently page 262) shows what you want.
There is a push/pull there but an On/On mini toggle switch is wired 100% the same.