Other than when using specialist HPC Ply or balsa wood, or expanded specialist styrenes a 3020 fitted
That's why I said this Toby,
I don't see any danger of HPC stopping doing the lite ply anytime soon, if anything I can see stocks increasing as he has new lasers in the R&D stage so always needs a good supply of consumables to use with them. Last time I spoke to Chris he has mountains of the stuff in stock and more on the way from China.
It is available direct from the supplier in China and Jennor Timber may well be able to get it for you but would probably mean minimum order quantities
There is a model making "Lite Ply" that has a balsa core but again cost is the biggest problem, it's a specialist market so the volume just isn't there to warrant crating huge amounts into the country.(it's only made in 3 factories in the world, two of which are in Spain)
My limited understanding of the Chinese special laser ply is that it is dried to a far further stage than western made ply hence cuts more easily.
Poplar plywood may also be a good option, it cuts far better than Birch ply but isn't as strong.
Normal (read@ low formaldehyde) Birch Laser ply of 9mm though isn't going anywhere on a 35 watt laser sadly
best wishes
Dave