You could always grind/file down the end of the shift lever till it's suitable. The decrease in leverage may affect the amount of force needed to shift, but probably not by much, and the price point of an Acera 3-speed shifter means replacement is easy if it all goes wrong.
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A race bike in any era is a highly personal choice that at its "best" balances the requirements of fit, weight, handling, durability and cost tempered by the willingness to toss it and oneself down the pavement at considerable speed. ~Bandera