Hi,
eBay is a really good source for a beginning collector. And if you are interested in vintage European restraints,
www.Cuffsland.com has some - but it's better to have a look at the "Sammlerecke (Collector's Corner) of
www.Cuffsland.de, because the German version is more up-to-date and has more collectibles.
Regards,
Guenter aka Atame
www.atame.info