Just in case anyone wants to do the same thing, I found a solution and wanted to let you know what I did. I used my Samsung Galaxy S4 smartphone as the USB host by purchasing a $4 cable from Amazon. It's an OTG Y-cable with micro USB and power USB. I obtained the free Android App called "Garmin uploader" by Sportablet. I connected the Y cable to the smartphone, the Garmin, and power and uploaded activities via the ST Garmin Uploader app. Worked perfectly--I can't tell a difference between this method and what I usually do with a computer.

My reasons for not using other methods suggested:
1. Buy a newer bluetooth Garmin: I didn't want to do this as the Garmin 510 is much larger and harder to read in bright sunlight. My 500 works perfectly, is small, and easy to see.

2. Use the Strava App on my S4 smartphone: This sucks the life out of the smartphone battery, which I'd like to keep available for communication or emergency phone calls if needed. In addition the Strava App doesn't do as good a job as the Garmin 500 with it's barometric altimeter and the Ant+ that connects with my existing Garmin HRM.

3. Save rides and upload to Strava when I get home: This is a tedious process after a 2 or 3-week vacation or tour, plus it's nice to still be able to see your daily rides and progress on Strava (as it is for your interested followers) as the trip progresses while at the same time travelling light without the weight of a netbook or laptop.

4. Use software to copy from Garmin Connect to Strava: This would require that I have a solution to upload the rides to Garmin Connect first, so still using some other technology to do that without a computer.

Total investment in this solution was $4 and my suitcase or pannier will be 2-3 lbs. lighter. Can't complain about that!