This is hearsay, I don't have first hand knowledge, but it's my understanding that Pete Allen is at an advanced age and his health is not allowing him to work any more. There doesn't appear to be anybody that is able and/or willing to take over for him, and the foundry is shutdown.
You haven't said which lock you have. Pete Allen cast parts for a number of locks over the years, most for other companies, but some were his proprietary locks.
You might check RE Davis first for parts. If you look at their page for locks (http://www.redaviscompany.com/locks.html), you will notice a number of locks listed as "On Hold". Pete Allen cast parts for all those locks. Is one of them like yours? If so, contact RE Davis and see if they have the part you need in stock.
Next you could check Track of the Wolf. They used to sell Pete Allen locks. Might be a long shot, but they may have some parts laying around.
That's probably an early version of Pete Allen's Tulle lock. R. E. Davis was assembling a later version before Allen shutdown his foundry. They called it a "French Fusil" Flintlock. Here is a link to it. https://www.redaviscompany.com/0046.html
Track of the Wolf Catalog #8 has it listed on page 145, Tulle fusil de chase flintlock by R. E. Davis, part #Lock-Tulle, but I checked on their website, and it's no longer listed for sale. There's some small details on the cock and frizzen that has changed since yours was made, but the photo in the Track catalog of the internals appear to be the same as in your photo above.
I would suggest you call R. E. Davis and/or Track and see if they have the part you need now that you know which lock to ask about. You will need to talk to them by phone as their online services may not show what the have as "left over" stock items.