I'm going to need an LRT-51-003, transfer case rear output flange tool and an LRT-41-012, transfer case oil seal seating tool. Are there any low cost aftermarket alternatives available in the U.S.?

 

Those tools are unnecessary. Use a universal flange holder for 51-003, or a pry-bar, and use an appropriately sized 3/4 or 1" socket for 41-012

For the socket, make sure to get one with thin enough walls so that it doesn't come into contact with the dust seal lip. Or harbor freight sells a ball joint kit that comes with a bunch of useful sizes for holding seals in place

 

Thank you.