Can someone get a mortgage for you co-sign if you can't get one for yourself because of credit score

Yes but then they are responsible if you can not or do not pay so it is hard getting anybody willing to co-sign

If someone would be silly enough to sign for you, that is, if they have good credit

If you cannot qualify for a loan yourself, its probably in everyone's best interest if you didn't get it. There is a reason you don't qualify for it.

Please think long and hard before getting a cosigner.

Whenever someone asks me this question as a loan officer , my usual advice is...

The "co-signer" should buy the property as an investment and qualify for the loan on their own. Then they should negotiate a separate "Rent to Own" contract with the erstwhile buyers. This way, their credit is protected and the "tenant's" credit history will get improved with a history of on time rental payments.

Of course, in this scenario, the buyer will have to demonstrate that they can afford the mortgage payments without consideration of any collected rents (unless they have several years documentable experience as a landlord).

Co-signing is rarely a good idea for the co-signer. I've seen a fair number of folks who have had their credit ruined (including parents of children who "own" the house) by being a co-signer.