Before you go and buy a chip, it might be worth splitting your bios into 4 and try booting from each segment, hopefully not every part is wiped, this will at least get your Xbox up and running again.
If that fails, the only other options would be to buy an LPC modchip, install and forget or get a 29 wire mod, install and reflash the TSOP. Then you can remove the modchip if you want.
You can't flash a TSOP using an LPC based modchip.