Aaah, that would have been good to know earlier... lol
The part numbers are different. If they were the same, they would usually have the same part numbers.
That said, for £28, go for it... Buy it and see if it fits...
Ok, I'm just completely lost now...
Exactly which part are you looking for???
Thanks for the comments. I was looking for just the exhaust pipe, not the silencer, so there's no brackets to worry about only its shape and dimensions. Ebay has some of the RX100 pipes under p/n 36LE46110000 and they do look similar being a sort of a shallow L shape with a loose flange fitting to mount to the engine and open where the silencer attaches.
Parts drawing sketches of both attached.
I should have added that if you click on the drawing, its name will be shown to distinguish between them, although they look the same.
Well, the good news is a SissyBar is indeed available for 2000 to 2005 models
bad news...not cheap!
https://www.ebay.co.uk/itm/374879990826?itmmeta=01HW004KJQAFSN3135SP9XB8RD&hash=item574896b42a:g:egoAAOSw4vNkIWZb&itmprp=enc%3AAQAJAAAA0G8DXxuvcuTkSOjSqvVeE%2BX%2FdCwJp2qK4dG1%2FgE9F%2F4QQ1K%2FWfuIIN7MoaQAgl3UhtSncHbTCbvUOJ3CxMuPe6Lm2fI%2FTlTvx7CbuMXfmsZhVC4EYsPoyTJdA6HVSJi544%2Fldhh007OUXQudEtueUo0CuW6yFSPhUtwNIWJwvdpY4oQ4IOE%2F2Bm%2F8%2FKncij2bFxANNB6c18DvOcSKQDWi8G4jAnZZmMVym7pv2LMAY3HqoMOFoC85qxA6p10cRiP0mX6UclE7ZKMD7mT0euekcc%3D|tkp%3ABk9SR7K5koDgYw
but now you know what you're looking for!