TR4 Fender mirrors were usually installed by the dealer, but could be ordered
from the factory (as Chip pointed out). It sounds as if you had the "flyback"
type mirrors (Stanpart 560632). Were they spring loaded? You mentioned that
they "swing up out of the way", indicating spring loading. As far as I know
(assuming you had the spring loaded mirrors) these are not in production, and
you would have to find them used. I have seen them at swap meets, so they're
out there. Start calling the vendors listed in the "T Parts And Accessories"
section of Hemmings Motor News and you might find a pair, maybe even NOS (but
prepare to spend the $$$ for NOS stuff).