Before you go searching for a switch that doesn't exist, and before you drill (and possibly chisel) for a chunky rotary switch, you should do this: Get a cheap and common two-way mini toggle, and wire it so you can directly compare the sound of one coil of your humbucker to the other. Then be honest with yourself. Can you really hear much of a difference in tone? In a pub band with drums and a couple of guitars, will you really use both of those sounds? IOW, is it really worth having that extra position?
If you still must have four positions, a rotary switch is probably your best bet.
My local sells them for a few bucks. Search ebay, amazon, etc. they'll be even cheaper. If you are mounting it through timber, it's unlikely you will have enough thread to have a shakeproof washer. So you'll also have to drill a small hole to accomodate the anti-rotation tab. Without some way of locking its position down, a rotary switch will loosen very quickly.
The other option is a slide switch- like the switches on a fender jag. You can get
4-position slide switches very cheap.