Try Ets Thomas Fils, Boite Postale no 2, 45450 Fay-Aux-Loges,
FRANCE, ph. 38.59.56.20 (don't know fax number).  The markers you
want are called Opalith-Formplattchen (umlaut over the "a" in
"plattchen").  They come in two varieties - one is just colours,
the other is colours and numbers (1-99).  The tags are attached
using gum spirits, which is included in the kit.