John Hopkins University continuously updated a repository of federal and private funding opportunities [1] that are intended for postdoctoral investigators. The opportunities are pre-sorted chronologically and alphabetically, and can be searched by funding [2] amount and subject matter.
Download the most recent list [1]The AlzForum also colleates a list here – https://www.alzforum.org/grants [3]
Dementia Researcher also has a list – https://www.dementiaresearcher.nihr.ac.uk/funding-calls/ [2]