I'm needing to replace an old 100 gallon diesel transfer tank and manual pump.

Anybody have any suggestions?

Northern Tool has some good options in stock, pumps and hoses, too.

Northern Tool

https://www.northerntool.com/categories/fuel-transfer-lubrication

You can buy online and ship to store for free if you have one nearby

JM Ellsworth

https://www.jmesales.com/transfer-tank-pump-packages/

Mine is an 85 combo toolbox with electric tank. Works like a champ. Made by South Texas Outfitters in San Antonio. It's in its second truck now and working great. Made of steel. Only thing I'd like to have on it is a sight tube to know volume inside, but I've never seen one on a transfer tank.

Previously I had aluminum tanks and integrity became an issue with hired help maybe not exercising the same caution as me when loading tools.