make a new trigger elsewhere.

It could be the brake disc bell/bolts, CV bolts if they are bolt in units, attach a new toothed wheel to a driveshaft, etc etc

There are many options.

If you need it to be accurate, once up and running you can buy DIY kits to build a circuit to +/-100% the numder of pulses so you can calibrate it to the speedo

Or you could weld a boss or install a new sensor directed at the toothed wheel, assuming this new crownwheel still has this provision ?