You can use the cable actuator module from any 1996~2004 truck or van, so that should be easy to find.
You still need to verify that you have the wiring for the actuator module.
Here's a diagram... It appears the module is under the hood, just to the left of the brake booster...
Find where the wiring for the wiper motor comes down out of the cowl, and follow it down. Hopefully you will find an 8 pin or so connector just taped to the harness there. That's the wiring for the cruise actuator module...
The Multi-Function switch comprises the turn signal stalk and emergency flasher switch. Four your 2004 van, it MUST come from a 2003 to 2007 van, not a truck or any other car. The pinout should not be different between cruise and non-cruise, there will just be several more wires populated in the cruise switch connector. You may be trying to install a MF switch from something else... ??
If you do not find that plug, then I'd recommend an aftermarket cruise control setup rather than trying to wire in factory cruise.
If the cable of whatever module you end up using is too short, you can buy the likely longer cable assembly for your van through GM. You can also just zip tie the actuator in place if you don't have the correct bracket.
Good luck!