Retire then work part-time

Personally I would call in when it is quiet and have a chat and casually mention that if they are looking for any extra staff or maybe have some vacancies coming up.

Go for it! They may not be able to pay very much, but if it is a nice place to work, that may be enough.
In the summer I offered to work in Waitrose for free, just for the opportunity to stand near the chiller cabinets

I think you could approach them face to face.

As you walk around urban areas, shops sometimes have notices in the window saying they have a vacancy. Have a look - you might see something else you fancy.

I would ask them directly. (When we retired and moved to the seaside there was a lovely bookshop I would have loved to have worked in. Closed down before I had a chance to ask!)

I would talk face to face to make general enquiries, and then follow up with a letter or email. Be guided by their initial response.
There may be opportunities for pre Christmas work, this may lead to a more permanent position.
Good luck x

Just pop in have a cofffee & general chat dropping the topic into the conversation.