Most MODERN power supplies automatically accept input from about 100 VAC to about 240 VAC with no "switching" needed.
Only older "transformer-input" type supplies needed the switch.

 US outlets for 234VAC circuits are NORMALLY NEMA 6 series outlets (this is NOT the same as the common NEMA 5 outlet you see in most houses).
 Cords for NEMA 6 to connect to standard power supply connections tend to be less common, and more expensive, than the very common NEMA 5 cords - there are quite a few folks that sell them though, check eBay, Amazon, Newegg for them.

 The cord you have the link to IS the type you are looking for - but way expensive, and you don't really need a "heavy duty" version as you're pulling well under 10 AMPs to fully power a APW3++ at 234 volts.
 The cord shown appears to be a NEMA 6-20 (20 amp) cord, you're more likely to want to use NEMA 6-15 cords and outlest (a NEMA 6-15 plug WILL plug into a NEMA 6-20 outlet, but not the other way around - like on NEMA 5 plugs/outlets the 20 amp version has one "T" type socket connector).
 With some digging you should be able to find applicable cords in the under $10 range.