I found that MS re-released their classic Intellimouse in late June. I had one of these way back in the early 2000s and no other mouse could match the scroll wheel behaviour I'd grown so accustomed to.
Found one of these things on the local Best Buy shelf and snapped it up. You should be able to find one there, or order them from the MS Store itself in a pinch. Very simple thing to use and still perfect for classic Halo on PC. Scroll wheel is great for fine tuning the stock manouvre node in KSP.
If I find more of these things, I'm snapping them up as spares.