Trailing arms may mean trailer axle mounts into bolt on bracket. One could use a spacer made from a steel square tube/channel that bolts between the frame bracket and axle bracket move the axle a couple of inches further below the frame. Or could even cut axle bracket loose if welded and then weld the extra tube/channel spacer between the frame and the axle bracket.
Put the axle an inch or two below the frame and you will pick up an inch or two of clearance. With the caveat that with the rubber compressed and beaten with age it will be easier for the trailer to bounce and use up that clearance. Also less torsion pressure keeping the tires
engaged with the road, would be sort of like having worn shock absorbers on a car but raising the car up to compensate.
As a short term solution for moderate usage it could work. Would duplicate work of mounting an axle in terms of labor cost but would avoid the cost of shop measuring and ordering the replacement axle for the time being.
No idea what they charge in your neck of the woods but around here welding service is about $50 an hour. So as long as it's a modest labor charge for an hour or two it might be a good option. Maybe one of the folks who have done own axle repair can weigh in on how long it should take to shim the axle down with a spacer.
What they CANNOT do is re-weld the arm onto the axle at a new angle, the heat from that would melt the rubber inside the axle tube.
I think one of the members who welded did something like that as a temporary measure to increase clearance of tire to wheel well and the ground clearance.