Another option would be phosphor bronze wire. It's a bit stiffer than brass, which can helpful at his diameter, and it still solders great.
You can buy it straightened. (There are probably other sources, but this is the one I am personally most familiar with.)
https://www.tichytraingroup.com/Shop/tabid/91/c/n_wire/Default.aspx
However I opted to buy it on a spool and straighten it. You get a fairly inexpensive wire straighting tool that does a decent job straighting the wire.
The pulling method mentioned above should also work, but does change the diameter a little and makes the wire stiffer (which can be good or bad).