So why not go down the injection or subcutaneous implant path? Buggered if I can find any information on it, so I could be wrong, but I figure it must be out there if I've got one in my arm -- why couldn't my dog?
You'll still get everything else, but without the risk of pregnancy...
*could someone correct me if I'm twaddling like an idiot? Please? *
It might help people here to provide you with the answers (or alternatives -- you clearly don't have all the information yet, so how could you make an informed decision?) if they knew WHY you wanted her ovaries intact but everything else taken out. It's like asking about tires, but not saying what sort of car or road you're planning on driving on.