This seems to be a had one, I've checked some of the usual Alfa spares suppliers.
Any way, the box is a generic item (prob. Bosch); I would try an auto factor or maybe eBay or the local Alfa specialist as they often break cars for spares.
I just posted one for sale in the classifieds from a 1969. I don't know if their the same, but here are some photos. The part # on the cover is 105.48.312.00. The smaller one is for the electric fuel pump.
Although the 69 and 79 main fuseboxes both have 10 fuses, they carry different part numbers. I think the difference is the mounting; the 69 has the fuses in a vertical position while the 79 fuses are horizontal.
Looking at the pics in the parts books, and the pic posted above, it looks like the mounting bosses (through which the vertical mounting screws go) on the 69 box would place the fuses in the vertical. I think that the mounting bosses on the 79 box are at 90 degrees to those on the 69 box hence the 79 box would have the fuses in the horizontal position.
Just going by what they look like in the parts books so I can't say for certain.
Here are some more photos. The top photo is how it mounts on the inner fender. The bottom photo is how it will look from the top. Send me an email. I'm sure we can work something out to be sure that this is what you need. [email protected]