Your mechanic needs to do basic troubleshooting to determine if it is actually the regulator that is at fault. Otherwise you are just rolling dice. The regulator is a separate part from the blower. I don't see one available here or at FCP either. All I see available on eBay are used OEM ones or new Chinese ones. You might need to find a different mechanic. When my blower went out on my '98 it was due to a melted fuse, since they used a fuse block contact with minuscule contact surface area. There are several things that can cause a fan to be intermittent.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra