Learned the hard way as part my key fob shell fell to the floor of the SUV when turning the key in the ignition.
JB Weld Plastic I used previously successfully on a expensive camera which a part was broken & obsolete.
I carefully spread some JB Weld Plastic in the inner & outer part of the fob shell where it was cracked, now it can be lightly sanded & painted.
Stronger than new.
The photo shows the JB Weld Plastic is a light grey when cured although 24 hours dry time is recommended for rough use.
Hopefully this will help someone in the future.
This is a great site, extremely helpful for first time Lexus owners as myself !!!
The finished repair project in second attachment, the battery can be changed.

 

I bought a replacement flip key, cut, on eBay for $22. I just installed the fob guts into it and it works perfect.

 

I suppose the difference is I paid $0.00 & waited about 20 minutes to be able to use it again.
I am confident it is much stronger than before although I'm using the FOB Key only to remotely open & lock doors & tailgate.
Especially here in the Great White North (Canada) with freezing temperatures & the unpredictable usually happens.
I'm using the other key for the ignition.

 

FYI, I made a solution for this after breaking two brand new ones right after buying my Land Cruiser (same key). I haven't had much traction getting the word out in the Lexus crowd, but the Land Cruiser and LX470 community has loved it.

Check it out:
http://yotamd.com/products/key_fob/Titanium3button.html

 

Yes, I had the same problem with my keys (the outer plastic case cracked apart), except instead of dropping the keys, the case cracked because I was turning on the ignition with way to much torque.

 

I spent about $10 on this product from Amazon. It isn't as well made as the yotamd referenced above, but similar idea.

 

Tried this out and the replacement shell fits and I was able to get the metal key tip and alarm transmitter to fit inside the replacement shell.

You may need a pair of pliers to remove the remaining bits of plastic that was insert molded over the key off though.

 

 

There was a post here someplace that will send you a cut key FOB, am sure you have to submit proof of ownership. Anybody remember?