i've had a same problem once when i worked on my '74 GS.
not being able to locate a good condition Stronglight spindle in 'right' price, i got a TA one off the 'bay.
while it had been listed as 118, it actually was almost 119, like 118.7543218345...
as far as i studied around, a TA 118 spindle totally would work with SL 93.

(however i ended up going with Campy Chorus arms + Veloce BB,
as my SL arms turned out unmatched)

there are some titanium version of SL 118 spindles around NOS, more expensive than entire GS bike itself...
good luck. it's a beatiful/fun/great riding bike.