Trying to find parts for a Thunder Tiger is like trying to pass a basketball out your colon. GOOD LUCK!! Typically, provided by Ace Hobby--but good luck getting ANYTHING out of them.
A side note:
I tore the cylinder head off a TT .91 once. Was trying to do an inverted pass down the runway and go under the tape that was strung across the runway on a couple volleyball poles. (Limbo).
I tore the head to kibbles and bits. Nothing salvagable.
It was $175 for a complete cylinder head. Valves, rocker arms, valve cover--the whole complete head. Shoot!! You can buy a NIB engine for $200.
Here's that link to your TT .91:
http://www.acehobby.com/ace/TTR9801.htm
Magnum parts can be found here:
http://globalservices.globalhobby.com/part/21097001.asp
Or, if that won't take you directly to the Magnum parts page--then go here and wade through the site untill you find parts support and Magnum engines:
www.globalhobby.com