A quick check on eBay shows a genuine oem Lexus key (in the bubble-bag) for $142. When you find someone to cut the key (it takes a special key-cutter), remove the transceiver... our local locksmith charges $25 for non-remote keys, and $40 for remote keys (for the same service, of cutting a key)... no kidding, finally figured out how to save that $15, by unscrewing the key, and taking out the transceiver. Programming the remote and security functionality is free, a great thread on each, is on here. So you should be able to do this for around $170.

 

FYI
Lexus dealer charges $15. to cut any key you bring in.

 

That's a good price, with the odd-ball double-sided internal-cut... I'd have to check locally, yet I'd be surprised if our local Lexus dealer is competitive. Walk up parts and service is almost non-existent... they all are about warranty and out-of-pocket service. When I get parts, I have to bring in the manual printouts and circle the parts I need... yet I'll ask locally, thanks...

 

I'm seeing an Ebay seller that will sell you a key and cut it for you, for $15:

https://www.ebay.com/itm/CUT-TO-YOUR-CAR-New-1998-2010-Replacement-Key-Shell-for-Lexus/302565672811?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D56426%26meid%3D7b265b110bde41ed899e8ea13d8434cf%26pid%3D100005%26rk%3D3%26rkt%3D12%26mehot%3Dag%26sd%3D292405598648%26itm%3D302565672811&_trksid=p2047675.c100005.m1851

Then there's a seller with a FOB for $21 $16:

https://www.ebay.com/itm/Remote-Car-Key-Fob-3Button-4C-chip-for-Lexus-GS300-GS400-ES3001997-2005-HYQ1512V/292405598648?fits=Year%3A2001%7CMake%3ALexus&hash=item4414bb59b8:g:H6EAAOSwYwZcRrLE:rk:17f:0

I was thinking it might be possible to transfer the FOB to the cut key's shell. Total cost = $36 $31 (+3 shipping!)