For two 20-25 lb. Shelties, the smallest Flexi brand leash was taken apart, and the cord replaced with braided Spectra cord from one of the cottage BPL companies.
Result – a 10-12 foot strong, retractable cord. Nite-Ize biners were added to a wrist strap so the leash could be clipped to pack, tent, bush or whatever.
Unfortunately, the newer model Flexis are more difficult to take apart and reassemble, but a few of the older models are still around in pet stores. The coil springs wear out eventually.
While Flexis have been critisized for walking dogs in high traffic urban areas, they work great in the backcountry, particularly on forest roads or mountain bike trails, where something wheely could be coming along fast.
A larger size Flexi and heavier cord would be needed for a larger dog. If you PM me, I will send you one of the old model larger ones – have no need for it. But if you want Spectra cord, you will have to do the replacing yourself.