How quick and cheap do you want this? You can accomplish your desired combinations if you're willing to re-order the listed positions. Check this out:
2 B + N
4 N + M
What I did was simply swap the Neck and Mid pickups. Of course, swapping the Bridge and Mid also works, you still get the important combo of B + N, but in the opposing position (2 vs 4, or 4 vs 2, depending on where you start numbering).
If that doesn't work for you, then we'll need to remove the standard Strat/Tele switch (it has only four (4) terminals on each side of the wafer) and insert a souped-up switch designed for this kind of work. In most guitar-modder circles, we call this a 'half-Superswitch', but you might find other websites that call it something else, I dunno.
The deal is, with this half-Superswitch, there is a unique terminal for each switch position. (A total of six (6) on each side of the wafer.) That lets you hook things up so that you can have your original desired order of combinations. Costs more, and takes more time to install, but no one can tell you what you have to do, only what you might want to consider.
Let us know how you want to roll.
Rule #1: All Lives Are Final. Make sure that the life you have just been issued is appropriate for your needs, before departing the womb.
Rule #2: In case you don't like the life you have, see Rule #1.
First of all, I am remiss in not welcoming you promptly. . .
Hello and Welcome to G-Nutz2!
The switch you show is a regular import-style Strat 5-way switch. With that switch, you are limited to what sumgai suggested- swapping the positions of the neck and middle pickups. This is easy enough,and is easily reversible if you ever decide to sell the guitar. You may find that you have to lengthen the middle pickup's wires a bit, depending upon how much slack you have to work with.
But if you insist on the N + B in position 2 or 4, then you're looking at a new switch as sg said.