This is slightly less expensive. I did buy tires from this place in the last 6 months and was a great transaction and the tires were recently molded.
https://www.tires4that.com/itemdetail/48D890
If you know the wheel mounting dimensions for your existing wheels you might be able to find comparable tires mounted on wheels through "Wholegoods". This is the sales department at your local Kubota dealer and is NOT the sales department.
If tractor is 4x4 you'll need to pay attention to overall tire diameter.
Sorry I can't be of more assistance.
Good luck
Added in Edit:
Check out Nebraska tire. They have a listing for $349
https://www.nebraskatire.com/agriculture
It's shown in the block titled: Compact Tractor Tires Discounted R1 and G1 Lug