I'm sorry to hear of your loss.
Yes, if you don't think you can get the information in time, file the return without it and do an adjustment later. Your husband's return will need to be mailed, as you can't NETFILE the returns of the deceased.
When did you husband die? If the death occurred between January 1 and October 31 inclusive, the due date for the final return is April 30 of the following year. But for the 2022 tax year, the due date is May 1st because April 30 falls on a Sunday. If you or your husband are reporting self-employment income, you have until June 15.
If the death occurred between November 1 and December 31 inclusive, the due date for the final return is 6 months after the date of death. If you or your husband were self-employed, and the death occurred between December 16 to December 31 inclusive, the due date for the final return is 6 months after the date of death. So you may have extra time.
The balance owing still must be paid by May 1st 2023.