Used Purchase 2000 zx3

I am buying a 2000 5spd.focus zx3 , it was the base model with cd no A/C and no power windows/seats ect...... plain to the nads. This car sat on our car lot for a year and one day I grabbed the keys for a venture to another dealer "delivering a dealer transfer" I thought the car ran ok and handled like it was on rails very responsive. I was sorta impressed but still thought it was running a lil ruff. I took the car on every dealer road trip from there on since it was kickin around so long just to make sure it was still running ok and it was but like every other time it was idling ruff and a tad hesitant with throttle response. Well after a few more months the car was gettin kinda dirty in and out from all the test drives so I decided to wash it. Before I washed it while I pulling it in the bay it was running terrible and sputtering so I took the spark plug wires out and had a look inside the housing and found a pool of water about 4 2-3 inches deep above the plugs. I blew it out with a air tool and let it sit open over night. Next morning I put the plugs back in and went for a drive and I will tell you that car had snap no hesitation and I was squakin the tires while moving 2nd and 3rd gear shifts awesome lil engine! Now I am buying the car lol .
My question is ............... whats a great way to seal the top of the plug housing so water doesnt get in there I like cosmetic stuff and dont wanna jimmy rig it if something is available? thanks in advance