As you can see by the photo, the original key fob (left) has had it. On the right is a replacement. Bought it off a vendor on eBay for like $8.50 for Qty 2. In the photo and in person, it looks great. I quickly found out, however, that the problem with cheap replacements, if you ever seek them, is that the quality control is not that great. With that, while the replacement fob shell looks good, the two halves don't even fit together empty let alone with a circuit board (and I tried all kinds of combos, including mixing the front of the replacement with the rear of the original using parts from both replacement fob shells). For the next replacement attempt, I might go with OEM or try out the "NuKey" fob that I've got sitting around somewhere that some of you might remember from a while back.
Typically, the grey plastic piece that connects the fob to the key is what fails first. One of mine broke after 5 years of use, the other failed right at the 10-year mark. I got one of the original, plastic fobs on LotusTalk. You had to disassemble the original fob, remove the circuit inside, and put it into the new plastic fob. My main gripe with this fob was that the buttons are a little harder to differentiate - I always had to really look at it to press the correct button to disarm the alarm and start the car. I can't find this fob online anywhere now.
When the time came to replace my other original key fob, I bought a rubberized one off eBay. This one is rubberized, and available in colors. I choose red, since my Elise is red. It's easier to set up, since you just slide the existing original fob into this oversized, rubberized holder, and the buttons are pretty much the same as you are used to. This eBay fob was $5.95, and has a woven leather lanyard. Be aware that, even though the eBay description lists this as a fob for a Lotus Elise, it says 'Toyota' on the reverse side of the fob.
Also, the red fob is on the orange side of the red spectrum.
If you insist on originality, it looks like you can get an 'original' key fob from eBay for $69.
Last Edit: Dec 31, 2017 11:20:00 GMT -5 by rcollum
Found a good replacement. It was like $8 for Qty 1 and, although a tight fit, the two halves went together. Including the first replacements, which didn't fit together, the worn out original and the replacement that worked (center), ended up with a lot of pieces parts, including, somehow, an extra lanyard (the grey pieces).