well, I think that Ed has suggested that for a quick "solution" (i.e. he likely doesn't consider it a problem?) the Fostex grille can be affixed to the speaker mounting screws with rare earth magnets glued to the grilles
of course if you're reveneering the cabinets, magnets could be recessed under the veneer and you're free to use any grille you like - including MDF frames with magnets in matching locations. 4 of the little 1/4" x 1/4" rare earth rod magnets are more than strong enough.