Hi,
why aren't you considering a zener-BJT voltage regulator, if you are not that concerned about the accuracy? By using the discrete approach, one would be more flexible by means of selecting the diode as well as the BJT. For further flexibility, you could even design a Darlington structure (two single BJT packages & 0 Ohm bridge). So you would be able to use a 5.6 V zener and a single BJT or a 6.2 V zener and two BJTs. But of course, this approach highly depends on your input voltage and your ambient temperature. If you are using opamps which accept input voltages of ~6 V (> 5.5 V), you could use a 6.2 V zener and a single BJT, which would have the best temperature stability.
BR