I have moss, C affinis and tons of red rotala.
Red rotala is so easy to grow I reckon you could plant it upsidedown and it would still grow! You can lie a strand longwise along the gravel, anchoring it with rocks or whatever, and it will grow up shoots all along the length.
It will cost you whatever the postage is. Overnight tracked will probably be somewhere between $10 - $18 between islands I imagine.