There are Coax-Optical converters that would do it.
You asked for the "easiest option". It's easy for me. It's another piece of gear in your bag, adds another cable, adds another battery, and another potential point of failure, but it works for me. You would think they would be flakey as hell, but I've recorded dozens of shows with them and never had a glitch that I remember.
I still have one I use occasionally, to patch an H120 out of the V3 or R4. Or run my R4 into my living room receiver.
There are various "Coax->Optical" converters on the market. Some are just Coax->Opt, some are both ways.
- I have the Hosa ODL-276a and it seems to work fine.
- I had the original 16bit ODL-276 (no "a") and it worked fine.
- I even used the el cheapo "gray box" without problems, but I don't recommend it.
- Another one is the "Maudio C02" (I haven't used that one, but it has a good rep)
- Most of my real experience using converters is 16/44, but occasionally 24/48 or 24/96.
- The ODL-276 (regular and "a") ran off a DVD battery (split cable to my A/D).
- The "gray box" ran off 4AA batteries.