Are you in the US? Parts availability is very much dependent on where you live.
Assuming US, you can get Daly BMS units off Amazon these days (for around $30 more than from China).
For Battery cells, take a look at
http://www.powerwholesale.net/ and see if they have what you need in stock in the TX warehouse. I know they just got a shipment of EVE 280ah cells because mine just shipped a few days ago. I've been dealing with Amy Zheng <
amy@docanpower.com> over there and she has been very responsive.