I ordered them through Aliexpress.com. It is kind of like Chinese version of Amazon.

Search: Heng Long T-90 parts or Heng Long T-90 tank parts.

I have ordered a lot of accessory parts through their site and have never had an issue. It does take two weeks or so to get the parts delivered but one can just about find every part for HL tanks. The small parts are cheap, it’s the shipping that can add up so I usually buy a fair number of parts when I order to make it worth the cost and time.