Make something you machinist you. I have done it many times. You need a piece of PVC ? or go to plumbing supply store get right pvc pipe fitting to fit the ball valve on one end, chuck it up in lathe and turn and thread other side. Take you 5 min. I have a 100 gallon tank buried in the ground I use for herring and eels. I just drop a small cheap sump pump in the thing occasionally and pump it out in 10 min. Has garden hose on other end which I direct at the neighbors shrubs. Here are a couple of the 7 I have
. First one is my herring transport tank. Second my boat livewell. You can see where I glued in a piece of PVC that was threaded for a garden hose on all of them. I also make and install a large 1.5 inch plug at the very bottom of all my tanks for easy fast draining. Dave you should be able to handle it. If not take it out and send to me and i will do for you.