You go to the local (to you) bank branch where the business has an account.
After contacting the business and getting their account number, making arrangements for the purchase, you present yourself with cash (easyer).
Tell the cashier you want to deposit X amount in that account, and get a receipt.
Return home, email or phone the business and tell them the deposit has been done, at what branch, at what time.
That is a bit of overkill, but it works well. The business can check their bank, and have your email to confirm things.