There are two separate issues .... getting the prescription and sourcing the meds. Some people have imported the meds into the US without a prescription, but I wasn't ready to try that.
I've said elsewhere that the clearest, simplest method is to come to Australia, and I still believe that, but it's certainly not your only option.
As for the length of time necessary, if your trip was properly planned it shouldn't take that much time anywhere you go. If you have the prescription in hand, good paperwork on the source and nature of the meds, and you've already started treatment outside the country, I can't imagine customs not allowing you to bring back your meds.
The Australian part of my trip was not planned. I intended originally to either get my meds in Thailand or travel to the source. Then questions arose about Mesochem selling to individuals followed by a lack of response from the Bangladeshi sources. When my Thai doctor wrote my script for Led rather than Dac I started considering coming here to get a different script. Also, I was concerned about bringing powders (APIs) back through customs and the compounding here means the meds are packaged in a standard pharmacy bottle with a proper label. But not warning Dr. Freeman I was coming means that the arrival of my meds has taken time. With proper communication this should not be so time consuming.
But again, there are other options. As for getting the prescription in the US, it almost comes down to doctor shopping. My insurance company would never have paid for that and the nature of my job didn't give me the time. If you want to try that, I'd suggest either an alternative medicine clinic or looking for a doctor that is presently prescribing medical marijuana as both are willing to think outside the box and defy traditional protocol.
I decided to just go where getting tests and a prescription would be easy and inexpensive. There are many such places. Depending on where you are, various places would be more workable. From the west coast Thailand is currently rather reasonable. From the mid-west or east coast you might prefer going to the medical tourism hospitals in Medellin, Colombia. Just look through this site to see many options. Look for gastroenterologists.
www.health-tourism.com/
Once you have the prescription from a US doctor you can either ship directly or travel to get the meds. Either way people are currently successfully getting their meds through customs.
If you do have to travel to get the prescription, I would suggest sourcing the drugs there as well and starting treatment before your return. It just makes it less likely they'd try to challenge the meds.