You can have old ones refurbished
I am interested in buying Romablok clamps to for my 1969 GTV and 1969 1750 spider.
If you are unable to find new ones, there is a gentleman who has a listing every month in the classified section (in the back) of the Alfa Owners magazine, who offers a reasonably priced service to strip and re-plate (with the proper yellow zinc) any old Romablok clamps that are mailed to him.
I haven't tried it, but I have heard that they come out looking quite nice. It may not be your ideal choice, but if you do find new ones later, other than the cost of paying twice, you can always switch them out.