Buy a handful of assorted (not in a packet) 470 uf caps from a local electronics parts shop, and I'll bet one or two of them will kick in at 490 uf
or... if you're in good with the staff and or a regular customer (like me

) bring in a cap tester/multimeter and explain what the deal is, and they usually say ok
and may help you sort some out too on the counter if the shop isn't busy
Best to go when it's the slow part of the day and the staff aren't 'multitasking'

FWIW: I discharge/short the unsuitable value caps after testing, before returning them to their spot in the shop
I do the same test biz with resistors and potentiometers when I need a freaky value or matched pairs/quads etc
It saves time, money, online purchase headaches, keeps the shop in business
and fellow electronerds in a job
