https://www.ebay.com/itm/Mercury-Lamp-Ballast-Cat-no-237-1371-for-1-250-Watt-H37-Mercury-Lamp/260992960226?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649 I just bought one of these , the seller accepted my offer !
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Ouch, the shipping cost!  5 times more than the cost of the ballast...