This is the type I am trying to track down. No luck. But plenty available with the upper brake light switch hole.
Yes that is the style we see on the vast majority of cars shown in the Unrestored Picture Thread here on the site.
Suggest a wanted ad here and elsewhere and also check to see if you can find a provider of rebuilt master cylinders if they are still out there and check with them. Know guys that have found what they were looking for by working with a parts house and sometimes having to order some to see what comes in. Often you will need to explain what your doing and they may or may not be interested in doing it but if you explain I've found that many are ok with the search and if you explain that you will buy more than one if found its a sell for them and something out of the ordinary that makes the day a little different for them. You can often resell the two or three extras and cover the cost of the one you need or even add to the restoration fund.
If you really get in the weeds you can even consider the date coding on the part if you want to go that far.
Good luck with the search