Try Northern Tool (northerntool.com) Northern Industrial Tools 12 V Halogen Driving Spotlights, Pair, clear, round, 3 1/2 inch, 55 Watts. On sale $9.00 per pair. Their Item No. 18814
They are a little smaller than the original driving lights, but fit in the space with the existing mounting bracket.
I cracked the lens on my original running light about a year ago and purchased this set from Northern Tool and was very happy with the results.