You need to go to your local hardware store and tell the sales clerk in plumbing you want a Fluidmaster 400A fill valve for a toilet. This will work in 99% of the toilets. You can easily change this out yourself in about 20 minutes or less. The instructions are very informative and this will cure your problem. Good luck. Here is a link that might be useful: Fluidmaster Fill Valve

tjdabomb is probably right. This means: 1) you need to check to see if there is anything stuck to the sealing part of the flapper or the porcelain rim it bears against that might prevent complete sealing; or 2) you need to check the chain or whatever it is that connects the flush lever to the flapper (sometimes they get a kink in them and the flapper doesn't go down all the way); or 3) you need to get a new flapper ($5). Toilets are pretty simple,,,you should be able to prove to yourself that the flapper is at fault by pressing down on it and forcing it to seal: the tank should fill up with your hand holding the flapper in place (don't worry...the water is clean!). Please report back after you investigate further. (One other less-likely possibility: I just fixed a neighbor's toilet with this symptom. The nut on the inside of the tank that holds the flush handle in place was a little too tight and the handle would sometimes stay depressed, so I backed it off about a quarter turn so it could move easily and return to the normal position.

Wow, I knew my local family-owned supplier was a gem; i.e. I needed a new lid for a particular circa 1963 Kohler toilet, in a sort of raspberry sherbet purplish-pink... AND THEY HAD IT! (I'm sure it was a std. developer install in my part of town, in the early 1960s.) Used, but mint. Only $25--reasonable! But back to the O.P., if you're a licensed pro, time is money... and it's also CUSTOMER SATISFACTION/PERCEPTION. Stop shopping. Stick to flooring. Give customer a new toilet, acceptable to them, slightly higher grade than the old one, write off the minor loss on your taxes. Horse trade the old toilet to the plumber who does the swap, and, being in the biz, I'm sure Mr. Plumber will eventually find a lid... bone is a pretty common color. PS: Your conscientiousness is commendable, and if a toilet lid is the most incidental damage you've ever caused gutting floors, you're at the head of the pack! Get the floor done, get paid. Quick perusal shows most Mansfield commodes are under $100. Smile, fess up, make it right, move on to the next job. Besides, everyone likes a new updated toilet to go with their new floor. ("Great news! You're getting an up to date NEW toilet, ON THE HOUSE!") Is the old one low-flush? Might be a REBATE for the new one. ;') PLUS, you'll get a GREAT recommendation if handled seamlessly.

Thanks for the suggestion. It doesn't really need to be "pumped out." We will be calling someone to advise how to keep the rain water out of the tanks. It might take some digging which is best done in the spring. We will probably muddle through until then, The big rains cause the alarm to go off. So if I pumped it after every rain, I would just need the pump truck to hang out in the driveway, because it pretty much rains every day.