Lots of parts are interchangable

2J's have TA21 carbs 5Ks have TA22 carbs

If the bike has a PGMII it's likely a 5K

There are lots of subtle differences. Best get a parts book and check out the pictures

This is the list I complied a few weeks ago

Moriwaki Man (NSR World)
David Silver (UK)
Lings (UK)
Yahoo! (Japan)
eBay
General google
Various breakers
I Love Motor (Japan)
CMS (Holland)
DK Motorcycles (UK)
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Why do things simply when you can complicate them