There are various software packages around for barcode printing directly from the AS/400. Maybe these will work with your existing printers, but you’ll need to talk to the software suppliers to be sure.
With the correct IBM package tou can create an AFPDS (Advanced Function Printing) print file using a DDS defined printfile with the barcode keyword. Check the requirements for this keyword in the DDS manual.
You have complete control without worrying how another package will interface your work.
Mos laser printers and copiers should be able to produce bar-coded documents from this AFPDS file