Yes, I've been hunting for this part for quite some time. I did find an inline vacuum check valve correct for '62 Olds a couple of months ago on ebay but the guy wouldn't ship to Canada. Anyway, your best bet is to use a universal check valve just like to type sold by Dorman Products (see photo):
Similar inline vacumm check valves from the mid-late 60s (GM NOS parts) are also available on ebay. BUT before you do anything, do have your system checked out for fluid leaks as previously advised. Good luck.