So this past number of months I needed a foglight and a right rear marker light for my 01 S Type. The ones on Ebay looked a bit tired, but decent price wise. However, by the time I paid the dollar exchange from US to the Land of the Frozen Chosen (Canada), along with the dreaded import duties and shipping, I paused and did some calculating.
I found the local Jag dealership had both either in stock or in the warehouse. While the foglight wasn't exactly cheap, the marker light was within $20 or so of buying used and having shipped.
So I ordered them from the Jag dealership. Nice to see there are still a few parts remaining in the system for these now older cars, although it does pay to watch the $$$ nonetheless.

 

Fog lights show up on aliexpress new.

For the rear market light, you are referring to the ones located on the fender? I am looking for one. If they are available and for that cheap I'll look into my local JLR dealer too.