What can I use to supply 220V DC to this motor?
The 220 VDC motor is (or perhaps was) chosen due to its cheap and straightforward driver implementation for any country with 220-240 Vac. Think of a triac dimmer with a bridge rectifier at the output and you have pulsating DC with approximately 220 Vdc (effective value, you could perhaps say RMS) for a 220 Vac input.

Here is a schematic of a simple version:


It says 115 Vac but the circuit would be practically identical for 220-240 Vac.

The diac-triac and associated RC snubber and potentiometer is identical to that of a normal light dimmer for incandescent lights.

There are plenty of commercial versions available in all price points. Here is one for inspiration: eBay link


Please note that this type of power supply is not galvanically isolated and both the +  and - output needs to be considered as hot AC at all times. 

As for "but it seems that 220 and 240 are treated as equivalent. Is that right?", it usually boils down to, at least for Europe, that the variation from 220 to 240 Vac from one country to another with usually 6 % specified tolerance was replaced with 230 Vac with 10 % allowed variation. You also sometimes see 220-240 V on some products.