Two years back I bought 54EC bonds ( to save tax on sale of property). This is how you buy other than the online option
Go to any bank such as HDFC, they have specific forms, or your own bank, fill in a form and hand over the cheque to them. The form will have an option if you want the same in demat or certificate option.
If your demat account is in joint name and if you are applying for the bond in single name this will be rejected and you will only get the bond as certificate.
I experienced this problem as my icici demat account was in joint name but applied for 54ec bond in single name. REC issued the bond in physcial form. The certificate will be couriered to you.
If you can buy it online nothing like it. I preferred going to bank option as I wanted receipt signed and sealed by the bank.