Personally, though it is expensive, I am a devotee of Signing Time.

How expensive?

What we initially did with Ada in terms of baby sign language never did
work, but she just seems to be starting to pick some up, even though we
don't really use them! She signs milk to get water, so she's a bit confused.
She's 19mths, and definitely has a speech delay, as far as we can tell, it
is just a case of being behind normal, rather than anything being actually
wrong, but she is keen to communicate through all sorts of means, and we
don't know whether behind normal will mean she will be speaking next month,
or next year and signs might be a good idea at this time, in case if falls
into the longer range category, or on the off chance that it turns out to be
a problem rather than just being slow.

Are these the kind of things it's possible to borrow from a library?

Cheers

Anne