By a strap, I assume you mean a leather strap? This watch likely originally was deigned for a metal bracelet. How would one go about fitting a leather strap to it? Just asking!
Okay, a bracelet. I have no idea if replacement bracelets for this Constellation have ever been offered by (for example) Ofrei, or other watch material suppliers. How much checking have you done, on line? Where all have you tried? eBay, maybe? Otto Freidl (is that same like Ofrei?) lists Constellation bracelets.
The only place that seems to have the correct bracelet Is omega but the cost is more then the watch is worth I was hoping to get a leather strap
The watch simply is not designed to accommodate a leather strap, in my opinion. The lugs on a strap model (I am fairly sure there must have been one with a strap) would be totally different. You may have no choice but to go for a metal bracelet.