Hard top liner

Anyone know where I can get a hardtop liner?

Are you referring to the “biscuit”?
The likelihood of finding one divorce from the top is a bit slim, I would guess.
I was faced with this when I bought mine & the price reflected that; what I did was to call upon the service of some self adhesive foam, bought to insulate a Land Rover hard top.
Cut & stuck with care, it functioned as an excellent base for the head lining trim, which I glued over it.
I was a bit stingy with the liner adhesive. It bagged after a while, so it came off easily, being replaced using a generous Lancashire helping of adhesive & not the Yorkshire sputter I used originally.
I still find greater enjoyment in using the pulley system I devices to lift it off & stow it, than driving with it on.
M

Thanks M 👍 

I did try something very similar, but after a few months, it was sagging, so I removed it, and now the condensation is horrendous. 

I  will try again with more adhesive. 

Try Lancashire adhesive, it is more generous & unlike the Yorkshire stuff, you leave the excess on & not scrape it off.
Think a really good quality bread, toasted, English buttered & Frank Coopers marmalade in the appropriate quantity.
M

The favourite marmalade of James Bond. 
It must be good in sticky situations..

I tried renewing the pvc/foam trim on the “C” panel on a MGB.
i gave it a liberal coating of glue (not too much or so I thought) and it tend to shrink into firmer lumps on curing and cured as expected where the adhesive was thinner.Spraying enough glue is the secret. I did manage to bond a section of the stuff to the deck head of the smallest room in a boat about 1M square. That was spread on with a spatula. The secret is definitely ensuring the excess solvent has had time to evaporate. A mask with carbon filter is a must.
You might try MARTRIM for recommendations