Something to try before you buy, get a bottle of CLR, and a metal clothes hangar, shut off water to toilet and flush holding handle down until water is below flush valve.
Flush valve is what the flapper seats on, now pour 1/2 bottle CLR into the flush valve, this will allow product to get into the flush rim of bowl.
Let sit overnight or eqivilent, then undo cloths hanger and keep the
part that hooks intact, the flush discharge holes are directional as you will see when flushing.
follow that direction when working hangar in holes, you will feel material like minerals and the like making it feel like your breaking porcelain, just keep on each rim discharge hole out until you have got them all.
Now turn water back on let tank fill and flush, you will be amazed how much debris will come into bowl, hope this helps, if not take 2 aspirin and toss in bowl. call a plumber in the morning!!
Good Luck & happy flushing