You can open NRO Trading Account with ProStocks.
NRI is no longer required to open PIS Bank Account for investment in Indian stock market without repatriation benefits. NRI are on par with resident Indian for all investment in listed equity shares on Indian stocks exchanges without repatriation benefits. Please refer the recent amendment in FEMA on RBI website at following link Foreign Exchange Management Act Notification and Foreign Exchange Management Act Notification in PDF
NRO Trading Account is subject to applicable withholding tax. This withholding tax normally known as Tax Deducted at Source and were hitherto deducted and deposited by your PIS Bank. Since Feb, 2016 requirement of PIS Bank Account is done away with for investment without repatriation benefits however requirement of withholding tax is retained for NRO Trading Account ( please refer above notification, schedule IV ).
Alternatively, You can give us undertaking / declaration from your Banker that they will compute and deposit withholding tax on your NRO trading and investment. Generally your banker will manage your NRO Bank Account also like NRI PIS Bank Account if you want your banker to deduct and deposit withholding tax.