I would say - if the trip is longer than 8 weeks or more trips to North and South America are planned, get a refillable 20 lb tank and appropriate fittings to connect to your stove.
If it's less than 8 weeks, buy green Coleman cylinders one per week (and again, appropriate fittings to connect it).
There "seems" to be no problems with running a butane stove on propane. Not the same gas (or not the same orifice), but it worked for me (with some odd effects that I wrote about, possibly related to burner or orifice diameter). If your butane stove will have real problems, then buy some cheap portable propane stove.
In any event, propane is in your future.