Hi Folks. Thanks to Dan and Zebede for the kind and generous offer but I have some really good news. I tried a different bike shop today and was surprised that they had some of the indicators. They had the Mark II for only $5 so I bought it. The original broken indicator was a shorter Mark I but the longer Mark II works just fine. So just for the challenge I took the original broken chain and drilled out the connecting pins, threw away the broken link, and put it all back together with a peened finishing nail. I will keep it for a spare. Hard to believe that parts for my 50 year old bike are still available. Sturmey-Archer sure built things to last.
Thanks again for all the advice, Grouseman