Brendan, you asked "and where do you find them".
Some places to look would be second hand shops, especially the ones that have stuff piled up everywhere. Antique shops often have a few razors though they tend to be pricey.
Some towns have monthly markets, I got a gold fatboy for $6 at one of them last year. Car boot sales are good for the odd razor too. Then there is the Buy/Sell on this site.
Ask you family and friends if they have any tucked away somewhere. Maybe some of the other members have favorite places they find stuff too that they would share with you.
Oh yeah, don't bother with charity shops like St Vincent D Paul. Those places aren't allowed to sell razors for some reason.