1. Section 125 cr.p.c. is quasi-criminal case and hence, you cannot force the court to comply with the criminal procedure code in letter and spirit.
2. But don't lose heart.
3. In maintenance cases, the courts observed more often than not that the contesting parties, both wife and husband tell lies out of their teeth about their income, educational standards, the reasons for living separate etc.
4. The court is concerned that whether the wife has got any source of her own income to determine the quantity of maintenance. If a wife, who has a huge bank balance, that came due to gifts she received from her natal home cannot become obstructive to seek maintenance from husband. So, bank account as such will not be much of help for the courts to find out whether wife is earning or not. Similarly, monthly remittance by her brother or father in her bank account will not render her ineligible to claim maintenance from her husband. Keeping these things in view, the hon'ble court declined your request to summon her bank records.
5. What you should do is to file an application, citing court judgments, directing the wife to file an affidavit and also all her bank accounts (pass books) for the last 3 years. If you know any particular bank in which she has an account, you should mention that. Once court gives such direction, she has to comply it. If she does not comply it, then you have to move the application summoning the bank record from bank officer. If the court refuses to give direction to your wife to produce those bank records or later on refuses to summon bank records u/s. 91, then you should move for revision petition.