Sierra Pine distributed Ultralight(Manufactured of Radiata in Australia and New Zealand) works just fine and is also low emission-I've used it for spoil board several times and suggested it as a Trupan substitute for the Northwest where it is much easier to obtain than Trupan.
Whittelsey in Miami probably still has Trupan-They have been a large stocking distributor for a long time. I'll check with my rep.