WTB -1973-74 Strat pickup, black bottom, 5.7K, buckley's

[Chinagraf]

Ok, 2 chances really, Buckley's and none, but if there was ever a place some boffin might know of, it could be somebody here..?
In late 73 and early 74 there were a few Fender Strats made that used a batch of pickups with staggered poles, but had black bottoms instead of the grey ones that were stock at that time. If anyone ever comes across one, I'm looking for one.
There is debate as to whether these were left overs from the black bottom stock they used up till 68-ish, or if a supplier simply used the wrong coloured bottoms on a batch and Fender used them anyway. I am of the opinion it was the second option as Fender didn't really hang on to stuff, but then again there was an over run of Tele necks around 77 that they used on guitars up till 1980-ish, so anything is possible.
I have a 74 Strat with 2 of these pickups, but the bridge is not the original, (it's a 74 flat pole) so I'm hunting one more. 5.7K resistance.
Thanks for listening.
Cheers.