Having been fed up with stopping every hour (or less) to thaw out my hands, I bought a set of heated grips today.
These are as good as sex (if you're married they're better than sex).
The brand is "Oxford", all wiring & switches are supplied (good quality) & it took twenty minutes to be up & running.
Variable heat control & maximum draw of 2 amps for each grip on full heat mean the old K7 rat can handle it okay.
The cost was A$130 which would be about $20 USA or3 euros