ItsDeductible was retired. There is a new feature that has been mentioned in the help and comments here to provide FMVs that may become available in ?March but I'm not sure you want to hold up taxes for that.
Otherwise you can use donation guides from Salvation Army or Goodwill.
There are also 3rd party apps like Deductible Duck which provide valuations but you have to pay for their service above a certain level; they may also claim to have import ability into TT desktop but there are limitations of the import format and you would still have to review each item in Turbotax (and avoid for TT Online as it breaks e-file).
Maybe @M-MTax has more
