This instructions is based on https://www.instructables.com/id/Binocular-Lens-Cap-Tether/?ALLSTEPS that i find very useful. Thank you very much for inspiring me number8wire. For me an old Telephone Extension Cord whithout use was more handy than an inner tube. and in the end it turned to be less bulky too.
Step 1: What Do You Need
1) Telephone Extension Cord
2) Super Glue
4) Lens caps
Step 2: Measure,cut and Pass
Measure and cut the cord according the extension that you desire. Glue it along the front lens cap as you can see in the pictures. The telephone extension cord fits well because it is flat .
Pass the other cord end trough the space between the focus wheel and the ocular, attaching it to the eye lens cap. I made a knot and glued . That is it, i hope this instructions can be useful .