Wow - thanks for all the ideas - since several of you have been kind enough to chime in, let me respond to your comments by poster:
MikeMI: a "Red-Green Bi-Color Common-Cathode LED" would be perfect and in fact an improvement (separate colors for hi/low side). Radio Shack had a two color LED but it had only two leads and I suspect was static for one color depending upon how wired. Assuming the LED you reference would keep the hi/lo sides separate (3 leads, 2 anodes, 1 cathode?), then this would be ideal (I assume I'd need to add resistors). Would you be kind enough to point me in the right direction (ideally to a place where I can order just 1 or 2). That would be my fall back plan (ideally would like to get my current solution to work as I've already drilled for the LED (which sits in a 1/4" hole)). As to your second post, I have to admit I have no idea what you mean by "(1N400x, where 1<=x<=7)" - I'm trying to learn as I go here but just don't follow that. But as you say, the LED does have an internal resistor and is spec'd to 12V and I have just the three parts (2 diodes, 1 LED).
SABorn: First, thanks for the schematic - I believe it is exactly what I've done. Yes, I typed too quickly on my second post - meant to say diodes when I was providing the no-doubt useless size info. Sorry about that. To your next point, I do want he LED to be on either hi or low - sorry if I confused on that. If it was just mean to be on one side of the switch I don't think I'd be having any trouble. For that matter, if I were willing to connect two separate LEDs for hi/low I'd be fine. Its just having one LED without connecting the two separate circuits sent me down the diode path based on a very hazy recollection electronics. A two color LED that would preserve 2 circuits would be fine but I've got everything wired for a single LED and two diodes and it would be great to get that to work - I just want to make sure I don't accidently knock it on while riding, don't really need 2 colors.
Reloadron: The switch is a simple toggle with three posts (middle off, down low, up high). Each grip has three wires (high, low, ground and the two sides are tied together (two high leads to hi switch pole, two low leads to low switch pole, two grounds to ground). I added separate leads from the high and low switch poles, inserted diodes, connected cathode sides of diodes to the anode of a LED (w/resistor) and grounded the cathode of the LED). I can meter around but it seems odd to me that, for example, the low post on the switch would show 12v+ when the switch is on hi (as it does per my metering as configured). And vice versa. Here's the product i'm using:
Heated Grip Kit
Not sure you can tell much from the site. I believe (based on nothing concrete) that there are two separate elements (or more likely the hi side hits 100% of the elements and the low side some lower %). If so, would the opposing circuit test positive when not switched on?? My concern is that I've either (a) put the low side to full power or (b) worse yet, connected two separate hi and low elements to create an ultra high (seems unlikely). I can test this but that will require me to cut out the work i've done - will likely do that tmrw.
Again, thanks so much for your expertise on this. And your tolerance of my ignorance.