Sourcing High Lithium Aluminium

I'm trying to find a supplier for a small amount of aluminium with around 2% lithium content, AL2099 or similar. I'm having no luck with suppliers in the UK only finding large round or rectangular bar stock.

I need to make a neutron discriminator target to test a neutron camera. The target would consist of increasingly thick layers of lithium aluminium interspersed with layers of acrylic. This would be placed in a neutron beam & the camera would see how thin a layer it could detect.

I'm thinking that, if I could get, say, 0.5mm sheet I could use layers of that to make thicker pieces.

Can anyone suggest a source?