Have you looked at LMC Truck? They will not sell a direct 1:1 for a suburban but do sell newly manufactured tanks for C/K trucks meant to replace the behind the seat tank with an under-bed tank. if you match your Suburban's frame dimensions to the right C/K frame I assume you could use one of those. They also sell newly manufactured tanks for Blazers which were previously mentioned as being a close match.
I posted below a link below from the GM Heritage website that might be helpful regarding chassis similarities. I believe you want a C for 2wd and a K for 4wd but don't quote me on that...
https://www.gmheritagecenter.com/doc...olet-Truck.pdf