Bad news

Sorry to hear about that.
I would definitly experiment on spare parts and styrene sheets.
What I would do is get a sheet of styrene the same size and thickness and try to heat some water, I wouldn't go to a boil. The try and sandwich it between a stack of books after heating it in the water for a few minutes.
Either that or a hair dryer. Try and apply gentle heat to loosen the plastic a bit. Then put pressure on it with heavy loads.
Maybe heat and resin in place. Heat it up and then glue it in place with resin to give it a bit of extra hold (assuming there is something to hold it with)
Thirdly - Call Tamiya - I once had a problem with thier 1/32 F4 and they shipped me a replacement part, no questions. Look on thier web site for a 1800 customer service #. What can they do - say no? You're no worse off and if they say yet the Yahoooo.
Good luck.. if I think of anything else I'll post again.