If you mean to find the Texas Instrument part #: TI 93045A4, it's not publicly sold. Replacement o3DS motherboards can be bought on eBay and aliepxress.
Thinking about writing a Dr Frankenstein fan fic.... Playing Dr with the dead, when science and lightning created monsters, the Dr theorized the missing ingredient was love, so he tries again. Theirs was a love born of science but the Dr couldn't resist Franks flesh!