That rim is an excellnet candidate for straightening, the shop you approached don't wnat todo it because they would have to make a fixture to mount the rim to whilst rolling it straight. Oh how I wish that when someone doesn't want to do a job tat they wold simply say so instead of inventing bullshit reasons.
Try another shop.
As to your existing rim, it is perfectly feasible to sweat a new lining into your rim, the trick of it is finding someone who is prepared to do it and who owns a lathe big enough to swing the wheel. In case to find such a person the procedure is to turn the existing lining true then make up a new lining, not finished to final intermal diameter, as sweat it in on a fairly tight interference fit - a lot of heat will be applied to the existing linig to do this.
Once the new linign is in, turn to finished diameter. The lining will never get hot enough in service to go remotely near disturbing the interference fit and in any event bot the new and old lining will expand at much the same rate.
A more practical suggestion - already offered by Wilcom, is to take your rim, brake plate and axle to a brake ship that doe relines and have them calculate the required oversize on the linings. Remeber the dimension they give you as you will need it again the next time you need to renew your brakes.