Northbend, As for a shop that constructs frames in Amsterdam i have heard that RIH still has the first shop they had in Amsterdam in a street called Westerstraat. I have not found it as of yet and i will ride past there again to find it and will let you know. As for the guys from Macbike on Manixstraat, they are very helpful and if Teo is there he can talk all day about bikes.
I dont know how you are traveling, however if it will be by car then you might want to pass a vintage bike restorer with some great bikes, frames and parts. I have not had the chance to go there yet but it is on the list for next month for me.
It goes by the name Vintage Bicycles Heeswijk and this is the address Heeswijk-Dinther, Noord-Brabant 0654272985.
If you look at the link below, it is set to a Colnago Master that he is selling and if you register you can contact him or it could be a she by mail.

http://www.marktplaats.nl/a/fietsen-...reviousPage=lr

I dont speak dutch so i mention it when i contact them for parts or bikes and they are good in replying so far.

This link shows what he has finished and is selling. I have seen photos of his work shop and i saw about 6 Gios frames hanging from the rafters. I want to visit him very soon.

http://www.marktplaats.nl/verkopers/2343435.html