Yes, in the old days all three strat pickups would have been the same, wound on a simple machine. As tastes progressed it became fairly common to buy an add on bridge pickup with more windings, for a higher level and "heavier" tone, or even a humbucker - but the neck and middle tend not to be different in construction.
However there's one thing in your case; the middle pickup these days can often be got in reverse wind/reverse polarity configuration. If you can get one of these for your strat it will sound the same as a regular middle pickup, but it will also cancel hum when the pickup selector is at the "in-between" position between neck & middle. (It won't cancel hum when used at bridge & middle in your case, as your bridge position pickup is already a humbucker.)
So, you might like to see if you can get a RW/RP pickup from the same maker as your current neck pickup, so the turns match for hum cancelling. But otherwise, any single coil will do fine.