I'm pretty sure you don't need EX500 perches. There's plenty of adjustable levers for factory 250 perches.
https://www.ebay.com/itm/124217315489
https://www.ebay.com/itm/132906601105
In fact, you can even use new-gen 250R 2008-2012 levers as well. Clutch-lever is exactly same. Brake-lever has narrower pivot on new-gen, but I just put a bushing underneath to take up the extra space and it works fine.