If it's that square steel tubing bumper, many RV supply places sell them. The problem I've seen is that they come as "tubing only," meaning you have to make brackets and weld them to the new bumper, or cut the ones off your damaged bumper and weld those to the new one. Perhaps somebody else here has found a bumper ready to bolt on, but I have not.
I'd suggest that IF you mount a spare tire, bike carrier, generator, etc. to the bumper then have reinforcement plates welded to the tubing then the frame brackets. That tubing is thin, and can tear at the bracket welds.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB
