For enamelling supplies in Holland you should try Ellen Goldman
http://www.goldman-arts.nl who is the distributor for Thompson
Enamels (leadfree enamels). I don’t know whether she sells kilns but
she is a very experienced enamel artist and very generous with her
You could also try http://www.zamaartclays.com who are based in
Jersey, Chanel Islands - they stock a range of Japanese enamels (that
are very finely ground so be careful when washing) and also stock a
very small basic kiln. Its chamber size is approx 30mm high x 100mm
wide x 130mm deep but it does have a built in controller and is small
and lightweight. I have one I take if I am doing a demonstration or
class at a venue outside my own studio.
In the UK there a plenty of choices - and with the current exchange
rate it may be worth investigating Vitrum Signum
http://www.vitrumsignum.com who have a fantastic range of all kinds
of enamelling supplies, including kilns.
I use all of these regularly and have always had good and helpful
service from them.
Best of luck with your search