Solder strippable wire is also called "Bicelflux wire" and it's a
polyurethane enamelled heat removeable insulation. Long ago, I bought
several small putups from a no longer remembered US supplier, however, among
others, it's available from:

http://www.greenweld.co.uk/acatalog/...melled_49.html

in a variety of wire sizes.

When the insulation is removed with a dollop of molten solder, a toxic gas
is released (in small quantities to be sure) and it ought to be done with
good ventilation in the workplace.

W4ZCB