You require a ON-ON-ON switch but you have only ON-OFF-ON under hand - Mod it

[kagliostro]

If you require a ON-ON-ON switch but have under hand only a ON-OFF-ON switch

and you are lucky (your ON-OFF-ON switch is compatible with the mod)

you can mod it to obtain what you require

http://www.harmonycentral.com/forum/forum/Forums_General/acapella-94/31545138-how-to-convert-on-off-on-dpdt-switches-to-on-on-on-selector-switch

You find the instruction on the above link

Franco