^^That's what I thought for years too, but is not the case anymore. There IS places that can reflash an '01 ECU believe it or not(took me a bit of proof to believe it, honestly)
Fortunately, in the past you couldn't reflash an '01 ECU but now quite a bit of dealers and locksmiths have the ability to do so. All you need to do is purchase a blank key with transponder. The problem is not every dealer or locksmith can do it.
I'm not sure if you're referring to, but I'm pretty sure Lexus still offers the "lost key program" where you buy 2 new masters, pay for the labor, pay for the stamp, and they give you a free ECM....all for ~$600 IIRC.
The other is the reflash and you may have to call around. There is a place called A-Any Kind Lock & Safe LLC, (421 E Nasa Road 1, Webster TX 77598. 281-338-9100) that can reflash and set you up with new keys. I know not all Lexus dealers will handle an '01 reflash, at least not the one close to me. There is an active member, Tommyfresh, that had his reflashed, so he may be alittle more helpful as I know he researched into it. The reflash would be your cheapest route, you just need to verify that a dealer or advances locksmith around you can do '01 ECU's.
'02 IS300 MSM LSD