Some buy used European Bosch or Elma headlights. I have a set of the Bosch on my LS. Very bright and long distance. For the 91S, I just use the slightly brighter Sylvania "Xtravision" 9004 bulbs, since that car is used mostly for developed and lower speed suburban and city streets. No deer around those near our house. And these bulbs do add a little more light.
Maybe for you, could use a set of high beam driving lights like jc96 has on his 164 in Italy.
The trouble with deer is that they can just jump up from the side of the road from lower down. That's exciting, have experienced that in Minnesota and Wisconsin.
89 Milano (wife's daily driver since 1989, Shankle Sport)
91 164S (my daily driver since 1994)
94 164LS (~Q) (trip Alfa since 2000)
72 Morgan 27 (water time since 1976)
previously owned since 1964:
62 Morris MiniMinor 850, 67 Austin 1275 Cooper S (Downton 3/4 race), 64 Giulia Sprint GT (1st red one made), 72 Fiat 128 Sedan, 75 Alfetta Sedan, 78 Alfetta Sedan, 78 GTV, 81 GTV6, 86 GTV6