Slow air leak on zero turn mower tires, what to do?

I’ve got slow leak on both rear mower tires on my zero turn. Size is 20 x 8-10. I have to put air in tires just about every time I mow. Should I just put some fix a flat/slime or put inner tubes? Would the slime sealant mess up the rims? I guess at some point I’ll get new rear tires…… saw a couple of inner tubes on Amazon for about $22

Thanks in advance for feedback