Power supplies

The supply must be a DC supply with a current capability of at least what you want to run the cell at and a voltage somewhere between 3.5 and 10 Volts. The positive is connected to the Anode and the Negative to the Cathode.
The power supply for making Sodium Chlorate or Perchlorate can be quite a crude affair or it can be as sophisticated as you like. It would be nice to have a supply that has a programmable current. This ideal supply would also have a fully smoothed output, built in Voltage and current meters, a Coulomb meter (measures Ampere hours) and be efficient.
To buy a supply like this would be expensive. A battery charger can be utilised as a power source. You may have to use the six volt setting as the current may be too high if you use the twelve Volt setting. It should be noted that the '12 volt' setting may not be 12 volts when you connect the charger to the cell. Chargers have bad Voltage regulation (an necessity when it comes to charging batteries and an advantage in our application) and the voltage will drop when you connect it to the cell. It will depend on the actual charger type and size of charger. If your charger has only a twelve volt setting and it is driving too much current into the cell you could consider putting two cells in series. You can also use resistors or diodes to lower the current into the cell
With battery chargers it is difficult to measure the current going onto the cell as they do not supply a fully regulated (smooth) DC current Voltage. You would need a true RMS meter to get a proper reading of the current going into the cell. Accurate measurement of current is not that important but you will need some indication of what the current is if you want reasonable accuracy regarding run times. If you can get a reasonable battery and connect this to the charger/cell set up this will have the effect of smoothing the current/voltage. Then an ordinary multimeter will give reasonably accurate measurements of the current.

An AC welder is a good supply to use for a cell but the output MUST be rectified before applying it to the cell. A DC welder will do too. The current will not be smoothed. The welder will be a constant current generator but its lowest current setting may be too big for your set up (size of Anode and cell volume). There is also the disadvantage of the welders high open circuit voltage. When you disconnect the welder it's output voltage will rise to maybe 80V. If, when your cell is running, one of the connections going to the Anode or Cathode gets corroded the voltage will rise across this bad connection as the welder forces in the constant current. This will lead to the connection failing by becoming red hot. This may permanently damage your Anode or perhaps cause a fire/explosion. A welder makes a good supply for an established cell and setup that has good connections, but it is a bad supply for experimenting with.

Computer power supplies are a cheap power supply solution for the cell.

A suitable supply can be made from a microwave oven transformer (MOT) and a rectifier.

See here for some info rewinding MOT's.

It should be noted that the current/voltage going into your cell with the power transformer and rectifier will not be a smooth DC current/voltage. A capacitor (a few micro farads per milliamp) can be connected across the cell so as to smooth the current and voltage. It should be noted that using too large a capacitor can lead to problems as the transformer may not be able to supply the high peak current pulses that are characteristic of capacitor smoothed supplies. The good old unsmoothed current does the job OK.
There are some scope pictures here of the current and Voltage obtained accross a cell with a simple transformer and rectifier set up.