You can do it. I would get come emery cloth, clifton glue and accelerator. Air dry the tube completely. Prep the back with Toulene, rough the entire area on the INSIDE and the patch. Determine the patch size and cut it from one single piece of fabric-prep as usual. Make two duplicate patches----one for inside, one for outside.
Start on the inside--apply glue and let dry to the inside of the tube and the surface of the patch. Here's the key though--work initially with a 2 inch length portion of the patch and inside tube --that will get it centered. If you get the first part right, you can then go from 2in to 4 in sections. Just work your way out until you reach the end. Once finished, let dry and repeat on the outside patch.
You can ALWAYS remove an incorrectly placed patch with a hair dryer on high and vice grips. No worries. Go to nrsweb.com and download their instructions on how to patch.
It will be tricky at first but after the initial part--it'll go rather quickly.
Dont give up on your trip!! Any mistakes you make can be rectified by you or others so you have really nothing to lose!