I just carry a lockring tool: NBT is no good for Centerlock rotors, so (depending on the bike) would only allow access to half my spokes that require a tool. Sometimes I carry the required 6" adjustable spanner[1] too, sometimes I don't. I reckon your chances of buying/begging the use of a spanner/ratchet are relatively high compared to specialist bike tools. A chain can be used as a chainwhip if you don't mind getting mucky.
Not sure if you can apply one of those kevlar bodge spokes without removing the cassette, but that might be an option.
[1] The trick is of course not to tighten the lockrings using a tool with more leverage in the workshop.