Buy a new rim
Line up the valve hole with the valve hole on the old rim, zip tie the two rims together
Transfer spokes 1 at a time to the new rim
Tension, true, ride like hell
I built my rear DT RR1.1 from an old Alex DA16 this way (1mm difference in ERD between the two rims.) The hub and spokes were fine, so why replace them?
BTW - 20,000 miles is awesome. I wear through a rim in under 10,000 (sand/cinders/road grit in the wet PNW)
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"I feel like my world was classier before I found cyclocross."
- Mandi M.