I'm in Ontario, Canada and we have a TOY & HOBBY chain here that carries a line of EXCEL Hobby Blades, which are made in Paterson, NJ, USA. They offer about 20 different blades and several very fine saw blades that fit a #11 X-Acto handle nicely. Seem to be in the model Railway section.
The one I prefer sells as a #13 Saw Blade, 5 in a pack, for $4.00. Code: E#20013
These are quite fine, and even tend to bend if you work them too hard, so I wouldn't
want anything much lighter.
No URL on package, but here is the full address if you wanna try and find a site on-line.
EXCEL Hobby Blades, 481 Getty Avenue, Patterson, NJ 07503, USA
Telephone: (201) 278-4000