HELP - blown sabretooh 5A - need one for Saturday!

Help,
I`ve just had smoke come from my sabretooth 5A and looking at the back there is one of the chips with a black mark around it.
Now one of the motors will only go in one direction! I really need one for Reading on Saturday, can anyone bring one along to either sell or lend for the day?
Its really important as my son has been looking forward to this day for a long time and he is severely autistic so trying to explain it to him that he can`t go is going to be very difficult.
Thanks
John
j.denny@live.co.uk