Hi John
You do not say were on earth you live, so I'll assume you live in the US.
The easiest way to buy a charger for N cells is to go to Radio Shack. You
need to buy a standard NiCd and NiMH charger (probably desktop) and a set
of 4 converters to make the N-cells fit in the charger.
If the RS people have no clue how to order these adaptors, ask them to
check the back of any rechargable N-cell pack sold by RS, it contains the
magic product number. Best to wait till you get the adaptors before you
buy the charger as they do not fit in all the chargers (esp. the small
ones).
One final note, the RS code will order you a PACK OF FOUR ADAPTERS, so
order only one - Yes I ended up buying 16 adapters :-(
On your second question (about running the HP-41 off a mains adapter),
there is no sensible answer. HP used to produce a rechargable battery
pack for the 41, but its a complete cludge as it uses minute cells which
are difficult to find, tend to leak and need recharging very often.
They allow the HP-41 to be operated using the same charger as the
other HP-41 peripherals (e.g. the 82143 printer), but, like I said,
they are expensive and too much of a bother. Its cheaper to buy
another set of 4 rechargable N-cells and simply swap them round.
**vp