Gosh Steve, first tubulars and now toe clips and proper cycling shoes! Good for you. A lot of folks here, for their own good reason, cherry pick the classic era. Ride a '73 Masi in 2005 dayglow Spandex? Fine. But not me. To me, classic cycling just that, not just the bike.
Shoes: except for the elusive and expensive Reynolds in the UK and Carnac (France) which I think has given up their two classic cycling shoes, your best source is eBay. I've gotten about four pairs that way. As long as you know your European size i.e. 45, 46. Most of these, like the Detto Pietros, use cleats but I am one of those who gets along nicely without them. I don't know if you can use any modern type cycling shoes with clips... they are usually so damn ugly, I'd rather go barefoot! But do check eBay. There are usually 3-5 pairs of Dettos a week listed. And if you find your size, stock up!
Next... wool jerseys, shorts and cotton racing caps.. oh and gloves too. After years of looking, I finally got a pair of NOS Italian leather cycling gloves with BUTTONS not that newfangled velcro! Bliss.
Peter Kohler
Washington DC USA