Forgive me but I'm not clear from the note which Testors paint you're looking to match; the only semi-gloss white available in the bottle that I'm aware of is/was the Model Master #2143 RLM21 semi-gloss white. That has an equivalence with Humbrol #130, which is also a semi-gloss, or satin, white. Other than that, it seems gloss white is the alternative, over-sprayed with a satin clear to get the sheen you may be looking for.
In the lacquer world, the choice is not much better. GSI's Mr. Color line has both a gloss and matt white, as does Tamiya's new line of bottled lacquer paints (the LP line). Same for AK Interactive's Real Color line of lacquer paints - gloss and matt. Almost all of these lines feature various clears for over-spraying - gloss, satin and matt. I can't comment on acrylics, as personally I'm not a big fan.
If you're looking for a semi-gloss white straight out of the bottle, maybe give the Humbrol #130 enamel a try, and see how that works. Hope this helps.