I don't think you'll be able to find industrials to replace your rear turfs anywhere. I believe the B2150 ratio is the same as the B8200 and you'll need to change the fronts also. 12.4 x 16 rears and 23 x 10.50 x 12 on the fronts.
What size tires are currently on the rear of your machine, Once we know that then it may be possible to find an R-4 tire that has the same height and width characteristics as your current tires. If an R4 tire is not available for your rim size you may have to switch to a different rim size, The critical thing is getting a tire that has the same circumference so that you can use your existing front tires.
Replacing your rear tires with an exact height R4 tire is based upon the assumption that your B2150 is 4x4, If it is 4x2(rear wheel drive only) the tire height is not as critical.
You may not be able to find an R4 tire in your desired height but you may be able to find a light truck tire with an aggressive tread pattern that will wotk for you.