Or, take the switch apart and stretch the little metal spring back out and clean the contacts all up. Mine was acting up and I cleaned up the switch and it has been working ever since.
The switch melts on the inside so no sense in buying a used switch that has just as much internal damage. Jeep doesn't sell just the switch new you have to buy the entire kit. At least with my 97.
You can, in fact, buy the OEM switch by itself, as well as replacements from several aftermarket brands. If you rewire the light circuit (bypassing the auto-off with the high beams, which means you need to kill them manually to stay legal on the street), you shouldn't burn up switches periodically.
Some quick searching yields the following part numbers for the TJ/XJ fog switch for 97+
5080861AA
56007247
Autozone SW 1935
Advance BWD S22030
NAPA ECH FL135
RockAuto Airtex/Wells 1S1808
SMP DS1082 (Standard's part may be discontinued, but it used to be available from RockAuto and Summit Racing among others).
You can buy the OEM switches from any Jeep parts retailer, as well as individuals and dealers on ebay (Towbin Dodge- the "King of Cars" folks, were the cheapest dealer on switches, at least for a while- they're also on ebay), and, you can buy simpler knockoffs, which come with a pigtail to simplify things if you don't mind the lack of OE symbols/illumination, like these...
http://motors.shop.ebay.com/__?_fro...J+Wrangler+1997-2006+Accessory+Rocker+Switch+
And you can always take your chances with a used switch. Around here, I can't find TJs or 97+ XJs in the yards, and I've seen a lot of guys asking nearly as much for the switches they yank out of junkyards as the NIB OEM switches cost.