My '88 3.2 Carrera had a secondary 'high intensity' screen wash bottle near the bulkhead hidden under the carpet on the inside of the n/s front wing. It was only very small in capacity, but one might be worth hunting down.
Whilst it had it's own switch scattered somewhere on the dash, I'm sure you could wire it into the conventional stalk. I'm surprised there isn't one already on your car - maybe it was an '88 model thing?
I know they are also fitted to 964 Turbo's

and I'm certain that's what they used on 964RS's too.
The true lightweight option

.
2006 RHD 997 Carrera (but DDK remains in my heart - also now no longer)
1972 LHD 2.4T with '73 2.4T CIS motor - gone to a new DDK home
1994 RHD 993 Carrera - gone!
1968 LHD 911L - was the Wife's but now in new hands
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