Ferrules for Stainless wire.

You need something that will crimp a near figure 8 profile to grip both wires. Pliers are likely to only give line contact grip on each wire but a std electrical crimp tool for the red/blue/yellow crimps might give a better result. If you have the decent ratchet type, make sure you find out how to use the ratchet release mechanism first as you might find the tool won't crimp fully and hence not release automatically.

I did something like this years ago using ~ 20 mm lengths of 1/8 inch copper tube. While figure of eight is ideal, with a bit more length than a standard ferrule it should work (assuming you are not loading to near the ultimate strength of the wire). I think I crimped with a mole wrench (which can apply a *lot* of force).

Toolstation do ferrules and clamp grips for that sort of wire...

Not Toolstation, but here are some anglers' ones for 1 mm wire, presumably single strand.

I've seen "figure of 8" aluminium crimps for stranded wire down to about

There was something on telly called Gripples - they might be of use. I don't know if there's a stainless one.

Those are for fencing wire. Rather larger than 1 mm.