Us XJ owners feel your pain, the 4 door Wrangler crowd has taken priority with most aftermarket parts manufacturers, rightfully so given the growing Wrangler customer base vs. the shrinking XJ/ZJ customer base.
I've built a plate system, similar to what Goose Gear offers, because no one could provide exactly what I want/need. Even when they were more relevant, ZJs had a more limited aftermarket support than the XJ, as these vehicles get older and older, we'll be left in the dust.
Goose Gear makes some universal drawer systems that you could set up in your ZJ, not cheap but as good as it gets for automotive drawer systems. You would need to build a sub floor, or plate, to mount the drawer to, or bolt it right to the floor.