I can understand why they don't have a hitch on the back! Just think how many law suits they'd have, if dumbo's installed a tow hitch, hooked up a cart, then went on to use it like they did with their old, conventional lawn tractor, etc. Would they try backing it with the cart on it? Oh, yes they would! And, do you think that just possibly they might turn the machine over right quick? Oh, yes! And, do you think the owner would sue the mower maker for his injuries, after the thing tipped over? Oh, yes!
The fact that a tow hitch is not installed keeps the law suits from happening. And the mfgrs. know that. And, if you did install a towing hitch, that will nullify the guarantee's and any chance you would have to sue for injuries or damages. Altering anything kills chances of suing, in most cases.
I'm not a lawyer, but those are the things/reasons why they don't install a tow hitch/bar/rear plate on a zero turn mower! JMHO: Rusty Jones

AM137381 Is the part #.

My Kubota has a hitch and is the best tow vehicle I have for around the yard. I towed a 12 foot trailer full of shingles once. Anyway you do have to be aware of the tongue weight and don't ever overload it from that standpoint.

When I went shopping for a new ZTR a few years ago, all the big names offered a hitch for them. They wanted you to pay more for it but it was available. If the factory makes it as an option, they won't void the warranty if you have it installed and use it correctly.

Sure you can use a zero turn mower for towing. It will pull or push just like a tractor, albeit one that turns on a dime. Remember to not use the zero turning ability at the extreme when towning and all will be fine.