RH outside mirror - light sensing??

1999 Blazer LS 2DR 2WD.
OK guys, help me out with this one... My outside mirrors are both electric & heated. When I bought my Blazer, the passenger side plastic mirror housing was broken. The only part of the mirror that is broken is the outside plastic housing, not the mirror it's self. I do want to replace it to make it look nicer.

The thing I can't seem to figure out is this... the rear view mirror & drivers outside mirror have the dimming (darkening) feature which I love having! Either the passengers outside mirror didn't come with this, has been replaced with one that doesn't have it, or it's not working on that side. Seems like if one outside mirror has that option, the other one would too. Right?

I've been looking at RockAuto for a replacement, but it seems that they only have "power, heated, w/o light sensor". My RPO code reads "DD0 MIRROR O/S, LH & RH, REM CONT, ELEC, DEFOG, LT". Does that mean the passenger side should have light sensing too, and if so, where can you find a replacement that has that feature? Is there a way to purchace and replace the plastic housing only? I've thought about after-markets, but my first choice is to replace the passenger side with the auto-dim feature. Any answers, suggestions or opinions would be appreciated!

Thanks,
Kristi

Don't think the pass side had a dimmer/light sensitive mirror in it, only drivers side as my LT does. Been awhile but look at the wire connector plug and dimmer option has more wires in it (think 5 vs 4 for non) but you will have to pull the door panel to see. If fact my drivers side is always dimmed now (never did figure out why) but think the sensor is in the mirror - and I am used to it now - but only drivers did this.