Roger-that on the one-and-done.
If you go the fixed resistor route, you can gain some variability with a simple on-off switch. In the example below the switch shorts/shunts 2 of the resistors. Thus you can select between 5 Ohm (switch "on") or 15 Ohm (switch "off). I figure you're removing the 9V battery snap connector shown in your photo and perhaps even the on-off switch...in which case you could re-purpose the switch into a hi-lo volume selector!
Otherwise, on-off mini toggle switches are fairly inexpensive even from US sellers. The eBay listing above even has pre-soldered wires.