Best bet would usually be akishop.jp in Japan who stock both Seimitsu, Brook and many other nice items. My last few orders from them have taken a very long time (2-3 months) and this was pre-Coronavirus.
My last order was a mess and they ended up forgetting to ship me my sticks after 10 weeks of waiting, and only shipped all the other random cab parts I had ordered. It sorted itself out in the end, but not without opening a PayPal case. So yeah. Just be warned. They’re good people, just take a very long time. The benefit with them has always been that their shipping to Australia is very reasonable.
When ordering sticks on eBay, there’s always the possibility of getting dodgy Chinese knock offs. Best advice would be to buy from someone who is involved in the community, such as FocusAttack or ArcadeShock where you’ll find other goodies to help ease the pain of high shipping.
Good luck!