He needs to check with his attorney/trustee, as he might not be allowed to get new debt until discharge.
That being said, OpenSky and GreenDot are secured cards that he *could* open without a credit check that report to the credit bureaus and are recommended on here for rebuilding. My trustee didn't care so I opened a OpenSky account and have it reporting to the three bureaus.
Chapter 13 BK ✓ Filed 4/10/2020 ✓ Meeting of Creditors 6/4/2020 ✓ Deadline to File Claims 6/23/2020 ✓ Confirmation Hearing 8/11/2020
Credit scores as of 8/18/2020: EX: 554 | TU: 552 | EQ: 592