I've been a big fan of dorades for a long time. They're simple, keep 99% of the water out of they're properly designed, give a good amount of air to the boat, and can really spruce up your boat.
I'm not exactly pleased with the plexi top but as you've found out, dorade boxes have either been incorporated into the cabin tops or eliminated. So, if the dorades work, and they look butt ugly here's what I suggest:
Carefully look at the plexi top making sure it's in good condition, well secured and sealed. Make sure the teak is dry, inside and ouy. I'd remove the plexi top and sand the teak with 120 then 220 grit sandpaper. Apply a few coats of varnish, inside and out, and reattach the plexi along with a bit of clear silicone to keep it water tight.
You don't indicate if the dorades leak but since you've got the dorades off, I'd check the splash tube for cracks, leaks, or age.
I don't see a drain (on mine the drains about 1/2" x 1" on the aft outboard side of the box. That way any water that the dorade vent collects runs out rather than down into the cabin. I'd make sure the edges of the box are snug to the cabin top or you may get more water in than the drain can take out.
Finally, I'd look for dorade covers. In heavy weather I'll removed the vents and screw in the caps (looks like yours don't screw in), blocking any water from being ingested by the vents (or you can turn them 180 degrees from either the wind or course).
I've been on the hook during some tropical deluges with all the hatches and ports closed. I got a nice breeze and no water from my dorades. I think they're well worth the couple of hours to bring them back to bragging condition. Oh, and I'd see about finding a spare dorade vent. I know of a couple that have grown feet.