yeah find plug fittings for the hoses. Probably 3/8 JIC? Then you can use it normally although the loader will have zero power, it will be very fast acting. Then you can mow. Most Kubota's have 2 lift cylinders and 2 bucket cylinders. The two cylinders run off of the same pipe so if you just plug the hoses on one side, the other will still get fluid-twice the volume, so it'll be real jerky/fast....but it'll still kinda work. Kinda hard on the loader frame though.
Or just make you a metal rod to length, weld a pair of pin bosses on, lift the loader and insert the rod where the missing cylinder is. Basically a dummy cylinder that will lock that side of the loader in the up position. Plug the hoses and off you go.