I dont know if anybody is looking for incavare spares but i have found a proper Aladins Cave of bits, probably enough to build a new one
https://www.worthpoint.com/inventory/search?query=invacar+ac&categories=
If it was Blue Hylomar then I believe it was a Rover recommended sealant especially for joints where no gasket was intended to be installed.
https://hylomar.com/en/universal-blue/
I have used it every time I had the 2300 engine to bits to seal the camshaft carrier and it has never leaked or clogged the oil ways.