I don’t have a M 1908 Mannlicher – Schoenauer to compare magazine details, but I have 1900, 1903, 1905 and 1910 model rifles. Two may be seen in my old photo, posted by Rothammer above. The rotating magazine followers are all of the same basic dimensions and fit the bottom metal of t other models. Merely the grooves in the caseneck separating stars and the troughs for the bullets are carved out different. The photo shows a 1910 9.5x57 follower on top and a 1905 9x56 one below.

Imho It is possible to alter a 1908 8x56 M-S follower by careful and time consuming use of a Dremel and grinding stones to take the 9.5x57, though I never tried. The base and bullet guiding ledges in the mag body may need some grinding too. One little quirk remains: the mag botton of the 1910 is about 1 mm wider than the 1905. This would leave a .02” gap between metal and wood on both sides of a 1905 magazine in a 1910 stock. But as M-S magazines are fitted and held metal to metal onto the receivers, this should not affect function. In your place, I would try the conversion from 08 to 10. Alas, an ill fitting but working magazine is far better than no magazine at all.